“Then Abimelech came to him from Gerar with his adviser Ahuzzath and Phicol the commander of his army. Isaac said to them, “Why have you come to me, since you hate me and have sent me away from you?” They said, “We see plainly that the LORD has been with you; so we said, ‘Let there now be an oath between us, even between you and us, and let us make a covenant with you, that you will do us no harm, just as we have not touched you and have done to you nothing but good and have sent you away in peace. You are now the blessed of the LORD.’” Then he made them a feast, and they ate and drank. In the morning they arose early and exchanged oaths; then Isaac sent them away and they departed from him in peace. Now it came about on the same day, that Isaac’s servants came in and told him about the well which they had dug, and said to him, “We have found water.” So he called it Shibah; therefore the name of the city is Beersheba to this day.” Gen. 26:26-33
Genesis 26 with Isaac contains many of the same narrative elements as Genesis 20-21 with Abraham, including a treaty with King Abimelech. There are some notable differences as well, some of which may not be picked up on due to common translations, or perhaps predispositions.
First we see Abimelech brings his advisor as well, which may have made for a less intimidating visit than just the king and the commander of his army.
Abimelech refers to previous oath, as some translations read “let the oath between us/ourselves now be between us and you”. Common translations seem to imply that Abimelech makes no reference to the covenant with Abraham, as if it were disregarded. On one hand it is understandable to assume this considering what happened with Abraham’s wells getting stopped up after his death, but, as we learned in the covenant with Abraham, not even the king knows everything his subjects are doing:
“And Abimelech said “I do not know who has done this thing; you did not tell me, nor did I hear of it until today.”” Gen. 21:26
Abimelech is not only recognizing the previous oath, but making it more bold by adding a curse for whoever violates the oath, by the phrase “that you will do us no harm”, which was not part of the covenant with Abraham.
It is easy from a plain reading to assume that Abimelech is not a follower of God. I would disagree based upon his interactions with Abraham and Isaac, noting that he shows both a fear and respect for God by not taking Rebekah after what happened with Sarah. Additionally because he has had an interaction with God and now adds a threat of retribution to whoever (be it his own subjects or Isaac’s camp) violates the oath for harm, it appears he intends to uphold it as he placed himself knowingly under the possibility of divine punishment.