“He said: It is so that you shall take the seven ewes from me, so that it will be for me as a testament, that I dug this well” (Genesis 21:30). “He said: It is so that you shall take the seven ewes…” – the Rabbis and Rabbi Yitzḥak ben Ḥakora, the Rabbis say: Abraham’s herdsmen were arguing with Avimelekh’s herdsmen. Abraham’s herdsman were saying: ‘The well is ours,’ and the others were saying: ‘The well is ours.’
Abraham’s herdsman said to them: ‘For whichever of us the water rises by itself to water his flock, the well is his.’ When the water saw Abraham’s flock, it rose immediately. The Holy One blessed be He said to him: ‘You are a model for your descendants. Just as with you, once the water saw your flock it immediately rose, your descendants, too, when the well sees them it will immediately rise.’
That is what is written: “Then Israel sang this song: [Rise up, well]…” (Numbers 21:17). Rabbi Yitzḥak bar Ḥakora said to them: This21The lesson that the water would rise again for Israel in the future. is not lacking from this place:22You do not need to derive it from elsewhere; it can be derived from this very verse. “So that it was for me as a testament” is not written here, but rather, “so that it will be for me as a testament.”