Leviticus 25:2

The rest ( sabbathises sabbatum). The land was to enjoy the benefit of rest every seventh year, to remind God's people that he had created the world, and that he still retained dominion over it, (St. Augustine, q. 91, 92,) requiring the spontaneous fruits of that year as a tribute, part of which he gave to the poor. In the mean time, all creatures rested from their labours, and the people were taught to have an entire confidence in Providence. (Calmet) --- This law was given in the desert of Sinai, in the month of Nisan, the second year after the exit: but it did not begin to be in force till the Hebrews entered into the land of Chanaan. (Haydock)