In Shulchan Aruch 489:1 the Machaber says that after Maariv of the second night of Pesach we begin to count Sefiras HaOmer. The Mishneh Brurah there in Sif-Katan 2 says that one should count before “Aleinu” because “col mah d’efshar l’akdomai makdinan”. Meaning that as early as possible one can start counting, one should. He writes this is in order to fulfill what it says “t’mimos tehiyenu”. That want the counting the be complete and full and therefore each day we count as early as we can to have it be a “full day”.
The question was asked. Why did the Mishneh Brurah use the language of, “col mah d’efshar l’akdomai makdinan” and not that of “zrizin makdimin” (meaning one should be quick to do the mitzvah.) It’s normally the language used in order to evoke someone to do the mitzvah quicker, faster, earlier, etc. Is there is a difference in these 2 languages. Is there a reason the Mishneh Brurah choose one over the other?
Perhaps for this case, where the halachic principle is not merely the concept of zerizus, but rather the idea of temimus, the Mishnah Berurah did not wish to express the idea of counting as early as possible in terms of zerizim makdimin.