"And they said, 'We have surely seen' (Genesis 26:28). [The doubled wording teaches:] We saw the deeds of your father, and we saw your deeds; and just as the Holy One, blessed be He, was with your father Abraham, so was He with you. And therefore we said, 'Let there now be an oath' — that just as there was [an oath] between us and your father Abraham, so shall it be between us and you."
Abimelech Tells Isaac We Saw Your Father and We Saw You
Midrash Aggadah, Genesis 26:28
ויאמרו ראו ראינו. ראו מעשה אביך וראינו מעשיך, וכשם שהיה הקב"ה עם אביך אברהם, כך היה עמך, ולכך אמרנו תהי נא אלה שהיה לנו עם אביך אברהם, כך יהיה בינינו ובינך: