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Ki Teitzei – Weights and Measures in Halachah

You shall not have in your pouch (possession) a stone and another stone, large and small.  You shall not have in your home a measure and a measure, large and small.  (Devarim 25:13-14)

Since the foundation of society, weights and measures have played a central role in the world of commerce. Because of their basic importance, we are able to trace a long history, spanning thousands of years, of attempts to regulate the use of weights and measures. As we will see, the Torah has much to say about this issue. Moreover, in modern times, when weights and measures are commonplace in  every home, the laws of weights and measures apply not only to vendors and tradesmen, but are relevant even to the ordinary householder.

The Severity of Weights and Measures

The Torah, in our Parashah, forbids the use of inaccurate measures: “You shall not have in your pouch (possession) a stone and another stone, large and small. You shall not have in your home a measure and another measure, large and small. A perfect and honest stone shall you have, a perfect and honest measure shall you have, so that your days shall be lengthened on the land that Hashem, Your God, gives you” (Devarim 25:13-15).

These prohibitions come in addition to the instructions found in the book of Vayikra: “You shall not commit a perversion in injustice, in measures of length, weight, or volume. You shall have correct scales, correct weights, correct dsy measures, and correct liquid measures – I am Hashem, your God, who brought you forth from the land of Egypt” (Vayikra 19:35-36).

Offences of weights and measures are temptingly straightforward – a weight or measure can be slightly corrupted, under the assumption that the buyer will not notice, or by convincing himself that buyers will willingly forego such small deviations. The Torah thus addresses the issue of weights and measures with particular stringency and severity.

The Gemara (Bava Metzia 61a; Bava Basra 89b) presents a number of ways in which vendors deceive their customers by using imprecise weights and measures, such as one who “soaks his weights in salt,” or one who uses the same rope in the summer and the winter, in spite of the slight variations in length caused by changes in the weather. Of course, the deviations caused by salt or by weather conditions are slight; yet, the Torah is particular over all acts of deception, even when the difference is but small.

In fact, Kessef Hakodashim (Choshen Mishpat 231:1) writes that the transgression of weights and measures is more severe than other means of deception, because the buyer relies on the seller, and will rarely be able to ascertain the precision of the seller’s weights and measures.

On account of its severity, a number of opinions maintain that the transgression applies even if the buyer is willing to overlook any inaccuracies in weights and measures. This is stated in the Tosefta (Bava Basra 5:4): “Rabbi Shimon said in the name of Rabbi Akiva … the precision of measures does not depend on the permission of others, for G-d has applied His Name to them.” According to one commentator on the Tosefta (Magen Avraham, no. 1), this implies that a buyer cannot “forego” the transgression, out of concern that the seller will similarly deceive others. Other authorities, however, maintain that the buyer may forego the error (Chasdei David, ibid; Kesef Hakodashim, Choshen Mishpat 231).

Transgression of Possession

Apart from the prohibition of gezel (theft) that transgressed by those who use such deceptive practices, the Gemara (Bava Metzia 61b) states that even the very creation of false measures, and their subsequent possession, transgresses the Torah prohibition of “You shall not commit a perversion in injustice, in measures of length, weight, or volume” (Vayikra 19:35).

Sefer Hachinuch (on our parashah , mitzvah 602), expresses the prohibition in the following words: “We are prohibited from keeping false weights and scales in our homes, even though we do not do business with them, lest they be a stumbling block before us. Therefore it is written (Devarim 25:13), ‘You shall not have in your pouch a stone and another stone, large and small,’ and ‘You shall not have in your home a measure and another measure, large and small.'”

This prohibition is ruled by the Rambam (Laws of Theft 7:3): “One who keeps an imprecise measure or weight in his home of his store, transgresses a negative commandment.” The prohibition is also stated in Shulchan Aruch (Choshen Mishpat 231:3).

There are some stores in which one can find two sets of scales. One set, which is calibrated with great precision, is used at the cash desk for weighing items and determining their price. Other scales, whose measures are often imprecise, are set aside for customers’ use, by which they can determine approximately how much of a certain food or product they wish to buy. Although the imprecise scales are not used for actual buying and selling, their presence in the store can involve a Torah prohibition, ((The actual prohibiiton will depend on the presence of a legal standard of weights and measures, which is clearly stamped on the scale. If the law requires all commencial scales to be stamped, and the inaccurate scales do not bear the stamp of approval, the prohibition is not transgressed (Rambam and Shulchan Aruch, as mentioned below).)) and sellers should be warned that every scale in the store must be absolutely precise.

This warning has been issued by the Ben Ish Chai, who writes that somebody in possession of such (imprecise) measures transgresses a Torah prohibition every moment—even during ne’ilah of Yom Kippur!

Weights and Measures at Home

The Gemara (Bava Basra 89b) extends the prohibition of creating and possessing imprecise weights and measures beyond the classic scale: “Rabbi Yehudah said in the name of Rav: It is forbidden to keep an imprecise measure in one’s house, even if it made into a bedpan.” Even if the form of the weight or measure is entirely unprofessional, it remains prohibited to keep it at home, for fear that one might come to use it in business dealings. This extension of the prohibition is ruled by the Rambam (loc. cit.)

Based on the wording of the Rambam, who mentions that even a bedpan should not be kept out of fear that it will be used in business dealings, Minchas Chinuch writes that the prohibition of possessing such an item is only rabbinic in nature. Minchas Chinuch adds that this is the express opinion of Rashbam (Bava Basra 89b).

However, Even Haazel (Laws of Theft 7:3) has pointed out that the wording of the Rambam, which states the prohibition of the “bedpan” as part of the principle prohibition, actually implies the contrary—that whatever the form of the inaccurate weight, a full Torah prohibition is transgressed. This is also implied by the Rambam in his Book of Mitzvos (Negative Commandment 272), and by the Chinuch in our parashah , both of whom state the addition of the “bedpan” as part of the Torah prohibition. As to the Rambam’s concern lest possession should lead to use of the weight for commence, this concern does not necessarily imply a rabbinic prohibition, but can be interpreted as the rationale behind the Torah prohibition.

Based on the prohibition of keeping inaccurate weights and measures in one’s possession, there is room to question the permissibility of everyday scales and measuring devices found in homes—bathroom scales, baby balances, food scales, tape measures, bottles with volume markings, and so on. Many of these devices are imprecise to begin with, and the inaccuracy grows over time, such that it would seemingly be prohibited to keep them is a person’s possession.

This, of course, is a difficult assertion. Can it be that all those who keep ordinary weights and measures in their possession transgress a Torah prohibition?

Baby Bottles and Tape Measures

Rabbi Shlomo Zalman Auerbach (Minchas Shlomo, vol. 3, no. 106), who was asked to address the question of a “baby scale” that somebody kept in his home, finds a possible reason for leniency in the ruling of the Gemara (Bava Basra 89b) and poskim (Rambam, Geneivah 8:4) concerning places in which the law requires all commercial scales to be stamped with a stamp of approval. Under such circumstances it is permitted to keep an inaccurate scale and measure, provided that it does not bear the stamp of approval.

Based on this ruling, Minchas Shlomo writes that the same principle can be applied to everyday weights and measures, whose very form bears testimony to their imprecision. Just as the (absence of a) stamp of approval ensures that inaccurate measures are not employed for commerce, so the obvious appearance of a measure as imprecise is sufficient to permit its holding.

However, is should be noted that Minchas Shlomo only relies on his rationale under the assumption that the prohibition of keeping such weights and measures at home is rabbinic—quoting the said opinion of Minchas Chinuch. As mentioned, the implication of the Rambam and others is that the prohibition is a full Torah prohibition. Yet, it is possible to apply the rationale of Minchas Shlomo even to a Torah prohibition—just as the Gemara does concerning the stamp of approval.

In addition, Minchas Shlomo points out that his rationale for permitting imprecise home scales might not apply to common tape measures. Unlike baby scales or a baby bottle, it is not easy to distinguish between precise or “professional” tape measures and those that are unprofessional and imprecise. Rabbi Auerbach therefore leaves the question of keeping an imprecise tape measure at home as tzarich iyun—a question that requires further scrutiny.

Finding Room for Leniency

Another approach for finding leniency is brought up by Kesef Hakodashim (Choshen Mishpat 231:3). Relating to measures used by householders to check quantities of produce, he writes that the prohibition of holding imprecise weights and measures applies only to those measures that might plausibly by used for commerce. Concerning weights and measures that are never used for commerce, the prohibition might not apply.

Once again, this line of reasoning can be applied to certain types of common weights and measures. A baby bottle is never used for commercial purposes; neither are bathroom scales. However, kitchen scales (especially electronic scales), might be plausibly used for purposes of commerce, such as in allocating the goods of a joint among neighbors who participated, or in simple sales (such as flour,  chickens, and the like) that are sometimes made between neighbors. For such instruments the question of prohibited possession remains unanswered.

Yet, perhaps there is room to extend the leniency to all forms of home weights and measures, by first defining the meaning of “precision.” Precision, for purposes of halachah, would be defined according to place and time. The precision required is one locale is not the same as that of another, and the precision of today is certainly different to that of a century ago. The obligation to ensure the precision of weights and measures fluctuates according to the degree of precision expected of the particular place and time.

With this principle in mind, it stands to reason that the degree of precision required in a store is not equivalent to the degree of precision required for a sale in a non-commercial home environment. Weights and measures kept at home are not subject to government regulation, and a neighbor wishing to buy a kilo of flour realizes that the scale used to measure it will not be as precise as those used by producers and stores.

Therefore, it would appear that weights and measures kept at home do not have to reach the degree of precision standard of stores. Rather, it would be sufficient to ensure the degree of precision normal for home weights and measures. However, if the prevision?? of a weights or measure should deviate from the normal degree of precision—which sometimes happens over time—keeping them in  possession would once more be prohibited, and one would be obligated to ensure that scales and measures are maintained at high degree of accuracy.

On account of the prohibition, and the difficulties in finding a halachic solution, someposkim have advised that home scales and measures should be labeled with the word “INACCURATE”. Minchas  Yitzcak (vol. 10, no. 149) equated marking as inaccurate with the above leniency of a place in which commercial weights and measures bear a standard stamp. Yet, he adds that they aren’t exactly comparable everybody knows that a balance without a stamp is inaccurate, but somebody in a rush might miss the “INACCURATE” label.

Nonetheless, together with the possible reasons for leniency mentioned above, it remains worthy advice to label in the above manner weights and measures that might be or become inaccurate.


  1. It is forbidden for a storeowner to keep an inaccurate balance in his store, even if the balance is not directly used for sales.
  2. It is likewise forbidden to keep inaccurate weights and measures at home, if their external appearance does not imply their imprecision.
  3. Poskim permit keeping possession of weights and measures whose appearance clearly indicate their being imprecise—such as marked baby bottles, bathroom scales, and the like.
  4. For home weights and measures whose appearance does not indicate inaccuracy, such as electronic kitchen scales, tape measures, and so on, one should ensure that the measure is as accurate as  possible. If the instrument becomes inaccurate, the halachic status of keeping the instrument is questionable, and at the very least, the instrument should be clearly marked with the word  “INACCURATE”.

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