Leviticus 25:4

The seventh year shall be a sabbath of rest. — Literally, the seventh year shall be a rest of solemn resting, or a sabbath of sabbaths. For the import of this phrase see Note on Leviticus 16:31. Like the weekly sabbath, the seventh year is to be the Lord’s sabbath. The soil is therefore to have a perfect rest.

Thou shalt neither sow thy field. — What constitutes cultivation, and how much of labour was regarded as transgressing this law, may be seen from the following canons which obtained during the second Temple. No one was allowed to plant trees in the sabbatical year, nor to cut off dried-up branches, to break off withered leaves, to smoke under the plants in order to kill the insects, nor to besmear the unripe fruit with any kind of soil in order to protect them, &c. Any one who committed one of these things received the prescribed number of stripes. As much land, however, might be cultivated as was required for the payment of taxes as well as for growing the barley required for the omer or wave sheaf at the Passover, and wheat for the two wave-loaves at Pentecost.