פירוש על ויקרא 25:8

שבתות שנים [AND THOU SHALT NUMBER] SEVEN SABBATHS OF YEARS [UNTO THEE] — seven Shemittah-periods of years (cf. Onkelos). One might think that one may keep seven successive years as “Shemittah” and keep the year immediately following them as the “Jubilee”, Scripture therefore states “seven years, seven times”, consequently you are bound to say that each of these seven years of release has to be kept in its proper time (i, e. at the end of six years of work) (Sifra, Behar, Section 1 1).

'והיו לך ימי שבע שבתות השנים וגו, the count of these years is not to be based on 12 lunar months per year only, but you will count hem as if regular years, the thirteenth month occurring at the same intervals as in your normal calendar considerations. The result will be that at the end of a Jubilee cycle, 49 solar years will have been completed. The same rules which apply to the sh’mittah calculation apply to the Yovel calculation. [since the farmer bases his activities on the seasons, and the seasons are controlled by the solar calendar, any other way of counting the 49 year cycle would throw the farmer’s schedule completely out of gear. Ed.]

Seven sabbatical years. Explanation: The sabbatical year is called Shabbos as it says (later 26:34), “The land will then be appeased for its Shabbosos.” So translates Onkelos, “Seven sabbatical years.” The proof [that “Shabbos” means “sabbatical year” and not “a period of seven years”], is because Scripture writes [afterwards], “seven years, seven times,” which indicates that [Shabbos] refers to [sabbatical] years and not to a period of seven years. [Otherwise, why should the verse repeat the same thing twice?] [Translating שבתת as “a period of seven years] would have been] similar to “Seven complete weeks (שבתות) they shall be” (earlier 23:15), which Onkelos translates as “seven complete weeks.” [See Re’m]