Midrash su Levitico 23:11

1) (Vayikra 23:15) ("And you shall count for yourselves from the morrow of the Sabbath, from the day that you bring the omer of the lifting; seven complete Sabbaths shall they be."): "And you shall count for yourselves": Each one shall count for himself individually. "from the morrow of the Sabbath": from the morrow of the festival (Pesach, on the sixteenth day of Nissan). I might think, from the morrow of the (literal) Sabbath, of creation (i.e., Saturday) — R. Yossi b. R. Yehudah said: "Until the morrow of the seventh Sabbath shall you count fifty days" (Vayikra 23:16) indicates that the entire count (from Pesach until Shavuoth) will (always) be fifty days, (which would not be the case if the Sabbath of creation were meant).

2) If I say (that the count is) from the morrow of the Sabbath of creation, then sometimes the count will be fifty-one days; sometimes, fifty-two; sometimes, fifty-three; sometimes, fifty-four; sometimes, fifty-five; sometimes, fifty-six (depending on which day Pesach begins). How, then, must I understand "from the morrow of the Sabbath"? As from the morrow of the festival.

3) R. Yehudah b. Betheira says: "from the morrow of the Sabbath": from the morrow of the festival. I might think, from the morrow of the Sabbath of creation. "Seven weeks shall you count for yourself" (Devarim 16:9) — a count which depends upon the determination (of the advent of the festivals) by beth-din, to exclude the Sabbath of creation, which is not dependent upon (the count of beth-din, its advent being known to all men.