Exodus 34:21

בחריש ובקציר IN PLOUGHING TIME AND IN HARVEST [THOU SHALT LEAVE OFF] — Why are ploughing and harvesting specially mentioned (since all work is forbidden on Sabbath)? There are some of our Rabbis who say that this refers to ploughing in the year preceding the Sabbatical year which ploughing passeth into (produces its first fruits in) the seventh year and to harvesting grain that has reached one-third of its maturity during the Sabbatical year which harvesting actually goeth forth into (takes place in) the eighth year, that following the Sabbatical year; and that this statement is intended to teach you that one must add part of the secular time to the holy time (i. e. that one must apply to a certain period before the beginning and after the termination of the Sabbatical year the laws applicable to that year in order to prevent its desecration). Thus, the following is what it (this verse) means: “Six days thou mayest work, but on the seventh day thou shalt rest”; but even with regard to the six days’ work which I have permitted you there are years when ploughing and harvesting are forbidden. This must be the meaning, referring to ploughing in the sixth year and harvesting in the seventh, and it cannot refer to the seventh year itself for it is unnecessary to make any mention of ploughing and harvesting in the seventh year being forbidden, for it is already said (Leviticus 25:4) “[But in the seventh year …] thou shalt neither sow thy field [nor prune thine vineyard]”! Others, however, hold that Scripture in this part of the text, is only speaking of the ordinary Sabbath day, as in the first part, and ploughing and harvesting which are specially mentioned in it as being forbidden on the Sabbath are mentioned to suggest to you the following: What is the characteristic of ploughing? It is an optional act (no such work being commanded anywhere in the Law)! So, too, is harvesting forbidden on Sabbath only when it constitutes an optional act! There is, therefore, excluded the harvesting of the barley for the “Omer” (cf. Leviticus 23:10: ye shall reap the harvest thereof) which is obligatory and which therefore supersedes the Sabbath (occasions a suspension of the Sabbath laws) (Rosh Hashanah 9a).

שֵׁ֤שֶׁת יָמִים֙ תַּעֲבֹ֔ד וּבַיּ֥וֹם הַשְּׁבִיעִ֖י תִּשְׁבֹּ֑ת בֶּחָרִ֥ישׁ וּבַקָּצִ֖יר תִּשְׁבֹּֽת׃

Six days thou shalt work, but on the seventh day thou shalt rest: in plowing and in harvest thou shalt rest.