Listen to how carefully Abimelech phrases his request. In Targum Pseudo-Jonathan on Genesis 21:23, the king asks Abraham to swear by the Word of the Lord that he will not act falsely — with me, nor with my son, nor with the son of my son.
Three generations. The Aramaic paraphrase preserves the depth of the oath exactly. A king is not thinking only of his lifetime. He is binding the unborn. Abraham's word must outlive both men speaking it.
The phrase by the Word of the Lord — be-Memra di-Yeya — is the Targum of Pseudo-Jonathan's fingerprint. Oaths in the ancient Near East were sworn on the name of a deity. Here the oath is sworn on God's active, relational presence, the same Memra Abimelech named one verse earlier.
And notice the ethical reciprocity. According to the kindness which I have done with thee, thou shalt do with me. The king is not demanding gratitude. He is asking for chesed returned for chesed given — covenantal behavior between peoples.
The Maggidim read this as a textbook on diplomacy. The takeaway: bind your word longer than your life. A promise worth making is a promise worth leaving to your grandchildren.