Sforno on Genesis 17:2/ספורנו על בראשית י״ז:ב׳

1ואתנה בריתי ביני ובינך, it is on this basis that I will establish My covenant between Me and between you. להיות לך לאלוהים ולזרעך אחריך, so that you will teach your descendants the lesson you have absorbed about Me.