Ramban

AND YE SHALL COUNT ‘LACHEM’ (UNTO YOU). The meaning thereof is similar to the expression And ye shall take ‘lachem,’ thus establishing that the counting [of the forty-nine days of the omer] and the taking [of the lulav, ethrog etc. on the Festival of Tabernacles] be done by each and every person. Thus the counting must be done by word of mouth, and he should mention the number, just as our Rabbis have received it by tradition..” This is unlike the expressions and he shall count ‘lo’ (to himself) seven days for his cleansing; then she shall number ‘lah’ (to herself) seven days, Verse 28. [referring to a man or woman who suffered a flux, in which case the counting of the clean days does not have to be uttered by word of mouth], because if they so wish, they may remain in their impurity; they must only beware not to forget their impurity [and enter the Sanctuary or eat holy food in a state of defilement, which Scripture strongly forbids]. or zavah] is under no obligation to proceed with the purification. Hence “the counting” of the seven clean days which the Torah mentioned that they must do could not be in the nature of a positive act — counting by word of mouth — but merely a warning that they should not forget their state of impurity. However, in the case of the counting of the omer, this reasoning is inapplicable, since the observance of Shevuoth on the fiftieth day is not a matter of choice, hence “the counting” must mean by word of mouth. Similarly, And thou shall number ‘lecha’ (unto thee) seven Sabbaths of years etc. of the Jubilee, means [only] that you shall be heedful of the number so that you should not forget [when the Jubilee year falls, but the actual counting of the years does not have to be by word of mouth]. But in the Torath Kohanim I have found it said: 2:1. “And thou shalt number unto thee — in the court.” Now I do not know if the intention is to state that the Great Court [of seventy-one judges] is obliged [actually] to count the years and the Sabbatical cycles at the beginning of every year, and to recite a benediction before the counting as we do at the counting [of the forty-nine days] of the omer; or it may be that the intention [of the Torath Kohanim] is to state that the court should be careful in the counting of the years, and sanctify the fiftieth year., p. 144. Thus the number of days from the day of the waving of the omer until the day of the holy convocation [i.e., the Festival of Weeks], is identical to the number of years of the [seven] Sabbatical cycles until the Jubilee, and the reason for them is the same. Therefore ye shall number fifty days which means that one is to count seven weeks [comprising] forty-nine days, and sanctify the fiftieth day which he has counted [and make it a holy convocation], just as He said with respect to the Jubilee. This is the meaning of the word t’mimoth (complete) — [seven weeks shall there be ‘complete’], meaning that they be exactly that number, no less and no more, just as is the meaning of the expression: they shall be perfect, for anything additional or missing makes a thing imperfect. Thus the explanation of this section is that we are to begin counting the days in the beginning of the barley harvest, and bring of the first fruits of the harvest, of the fresh ears, a meal-offering unto the Eternal, and also to offer up with it an offering,. and to finish the counting of the days in the beginning of the corn harvest, as a shock of grain cometh up in its season, and bring of it a meal-offering of fine corn flour unto the Eternal, and to offer with it also an offering. This is the reason why He mentioned these offerings in this section, because they are brought on account of the meal-offerings which are the main [commandment] of these festivals, but He did not mention the Additional Offerings brought on these festivals [which are enumerated in the Book of Numbers], even as He did not mention those of the rest of the festivals.