Komentaryong Sumisipi para sa Levitico 23:25

Another reason why the Torah wrote בשבעתיכם is to disabuse the fools who thought that the words ממחרת השבת in Leviticus 23,25 refer to the Sabbath of Bereshit, i.e. the ordinary Sabbath, rather than the first day of Passover (compare Menachot 65). By saying "your weeks," the Torah makes it plain that the count started on a day which was subject to the terrestrial court to determine. The terrestrial court has no authority to change the date of the Sabbath, although it may postpone the day on which we observe new moons. We have a Baraitha in Menachot 72 where Rabbbi Yehudah also deduces the same ruling from the words in Deut. 16,9 תספר לך, "count for yourself." This excludes days over which our courts have no authority and which all mankind counts alike.