2 Samuel 9:10

shall till the land This arrangement suggests that Ziba was already in occupation of the land, so that the only change to him would be that Mephibosheth would now receive the fruits instead of David.

that thy master's son, &c. Though Mephibosheth himself was to be a guest at the royal table, he would require the revenues of this estate for the support of his family and household. It may be inferred from the number of Ziba's servants that they would be considerable.