Question:
If one wants to take on a hiddur mitzvah or something else bli neder, is it good enough to just think “bli neder” or must one verbalize it?
Answer:
Hello,
It is definitely preferred to say bli neder prior to accepting upon yourself to do a hidur mitzva. However if it wasn’t said, and you thought it, that is sufficient.
Best wishes
Sources:
ע’ ס’ כל נדרי פע”ב ס”ק ט”ז ז”ל “והובא בשם הגרי”ש אלישיב זצ”ל דכמו”כ די אם חושב במחשבתו שעושה כן בלי נדר’ אף שלא הוציא כן מפיו”.
