Charles Ellicott Commentary Leviticus 25:4

"but in the seventh year shall be a sabbath of solemn rest for the land, a sabbath unto Jehovah: thou shalt neither sow thy field, nor prune thy vineyard." — Leviticus 25:4 (ASV)

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 significance of this phrase, see the 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 labor was regarded as transgressing this law, can be seen from the following canons that prevailed 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 smear the unripe fruit with any kind of soil to protect them, etc. Anyone 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.