תּוספֿתּא אויף בראשית 26:1

As long as Abraham was alive, there was plenty, as it is said (Gen. 24:1), "And God had blessed Abraham in everything." Once Abraham died, "There was a famine in the land" (Gen. 26:1). Isaac came and [again] there was plenty, as it says (Gen 26:12), "Isaac sowed in that land [and reaped in that year a hundred measures]." As long as Abraham was alive, the wells were filled with water, [but] once Abraham died what does it say, but (Gen. 26:15), "And all the wells which had been dug [by the servants of his (i.e., Isaac's) father in the days of Abraham his father, the Philistines stopped up and filled with earth]." They said, since they are no longer filled with water, they will be a hazard should we stumble into them, and thus they filled them up. Isaac came and [again] the wells were filled with water, as it is said (Gen. 26:18-19), "And Isaac again dug up the wells of water, etc." and "[Isaac's] servants [also] dug, etc."