Charles Ellicott Commentary Genesis 21:26

"And Abimelech said, I know not who hath done this thing. Neither didst thou tell me, neither yet heard I of it, but to-day." — Genesis 21:26 (ASV)

I do not know.—This explains the reason for Abimelech’s visit. The king’s herdsmen had robbed Abraham of a well, a type of property jealously defended in the East because of its great value, and Abraham in some way had made his displeasure felt.

Abimelech, always friendly towards Abraham, by whose noble character he had been greatly impressed, comes to learn the cause of the coolness and to enter into a closer and more lasting alliance with the patriarch. With characteristic Eastern indirectness, he makes no complaint and speaks only of his wish for continued friendship. However, by alluding to his past kindness, he hints that this had not been received as it should have been.

Abraham fully understands his real meaning and tells him what had happened. Consequently, the matter is set right, and Abraham repays his previous generosity with gifts of cattle.