Comentario sobre Génesis 17:4

BEHOLD, MY COVENANT IS WITH THEE, AND THOU SHALT BE THE FATHER OF A MULTITUDE OF NATIONS. This refers to the covenant of the circumcision, as He will explain, “This is the sign of the Covenant,⁴⁰¹In Verse 10: This is my covenant. and after the covenant you will be the father of a multitude of nations.”
Blessed be the Lord! By Him alone are actions weighed, for He preceded and commanded Abraham to enter into His covenant to be circumcised before Sarah became pregnant so that his seed would be holy.

אני הנה בריתי אתך, "I am now doing what I had told you, to make the covenant actual."

אני הנה בריתי אתך, just as you have ben certain that when I said to you that I am א-ל שדי that I have the power to change the laws of nature, I am telling you additionally, that you will not only be the founder of one nation, but that you will became the founder of numerous nations. Both Yitzchok, Ishmael, and the sons of Keturah will al become important nations.