Charles Ellicott Commentary Leviticus 25:8

"And thou shalt number seven sabbaths of years unto thee, seven times seven years; and there shall be unto thee the days of seven sabbaths of years, even forty and nine years." — Leviticus 25:8 (ASV)

And thou shalt number. —Better, And thou shalt count unto thee, as the Authorized Version renders the same phrase in Leviticus 23:15.

Number seven sabbaths of years. —Better, count seven weeks of years . The seven days of each week represent that many years, so that seven weeks of years make forty-nine years.

Therefore, the explanation in the next clause is: Seven times seven years. The observance of the jubile, like that of the sabbatical year, was to become obligatory only when the Israelites had taken possession of the promised land . Moreover, since the first sabbatical year, according to the authorities during the Second Temple period, began in the twenty-first year after they entered Canaan , the first jubile was celebrated in the sixty-fourth year after they entered the land of promise.