3,697. Beginning Hilchos Shemittah v'Yoveil

Hilchos Bikkurim 12:24

Let’s say that a Yisroel has ten donkeys that are definitely firstborns which he inherited from his mother’s father, who was a kohein. The grandfather, however, inherited them from his mother’s father, who was a Yisroel. In such a case, the current owner should separate ten sheep for them. These sheep belong to him (rather than going to a kohein), so they must be tithed.

Hilchos Shemittah v'Yoveil 1:1

There is a Torah obligation to refrain from agricultural and arboreal work during shemittah (the sabbatical year). Leviticus 25:2 teaches, “The land shall rest as a Sabbath to God,” while Exodus 34:21 tells us, “You shall refrain from plowing and harvesting.” If someone performs any labor on land or trees during this year, he not only fails to perform an obligation, he violates a prohibition as per Leviticus 25:4: “Do not plant your field and do not prune your vineyard.”