What does Genesis 21:30 mean?
In addition to giving Abimelech sheep and oxen as a sign of the broad covenant between them to treat each other agreeably, Abraham has set aside seven ewe lambs for a specific purpose. Here, in verse 30, he reveals their exact purpose. He wants Abimelech to take the lambs as a witness that he dug the well that is in dispute between them. Earlier, Abraham complained about Abimelech's men taking over a water source which he had dug (Genesis 21:25).In broad terms, Abraham is offering to formally buy back his own well, in order to once and for all resolve the issue of who it belongs to. Abimelech apparently agrees to this, and the two swear their oaths in the following verse.