출애굽기 34:19 할라카: Sefer HaMitzvot

That is that He commanded us to count the the years and the sabbatical cycles until the Jubilee year, once the land has been conquered and we have controlled it. And this commandment - meaning the counting of the years of the sabbatical cycle is given over to the Great Court, meaning the Great Sanhedrin. For they are the ones that count each year of the fifty years, just like each and every one of us counts the days of the omer. And that is His, may He be exalted, saying, "And you shall count off seven weeks of years" (Leviticus 25:8). And the language of the [Sifra] (Sifra, Behar, Section 2:1) is, "I might think that one counts seven sabbatical years, one after the other, and then have the Jubilee. [Hence] we learn to say, 'seven years, seven times.' Both verses, then, are needed; if not, we would not have understood [the law.]" And the regulations of this commandment have already been explained in Arakhin. But it is only practiced in the Land [of Israel]. (See Parashat Behar; Mishneh Torah, Sabbatical Year and the Jubilee 12.)