Or HaChaim on Deuteronomy 16:9/אור החיים על דברים ט״ז:ט׳

1 תחל לספר שבעה שבעות, "you shall commence to count seven weeks." Why did the Torah repeat the need to count seven weeks? Perhaps the Torah meant that in the event that on the date in question the wheat had not yet advanced in growth to the stage when one could cut it with a sickle, and you may use left over wheat from last year's crop to present the new loaves (based on the word ממשבותיכם in Leviticus 23,17 (compare Menachot 83), you must still commence to count the seven weeks starting on the second day of Passover. This is how I have to explain the repetition according to the many authorities who hold that nowadays when we do not have the Temple the whole legislation is only a rabbinic decree. According to those who hold that the decree is biblical also in our times, the basis for such a ruling is the repetition of the words "seven weeks."