John Gill Commentary Genesis 26:28

"And they said, We saw plainly that Jehovah was with thee. And we said, Let there now be an oath betwixt us, even betwixt us and thee, and let us make a covenant with thee," — Genesis 26:28 (ASV)

And they said, we saw certainly that the Lord was with you ,
&c.] Not only while he was among them, by the fruitfulness of the land he sowed, by the increase of his family, his flocks and herds, but also since he was gone from them, in the valley of Gerar, and now in Beersheba: and we said ;
one to another, assembled in privy council, in which this affair was talked over and debated: let there now be an oath between us, [even] between us and you :
what was between us and your father, or between your ancestors and ours, let it be renewed and confirmed before us; so Onkelos and Jarchi; see (Genesis 21:23) : and let us make a covenant with you ;
the articles of which follow.