Commentary for Genesis 17:2

ואתנה בריתי AND I WILL MAKE MY COVENANT — a covenant of love and a covenant regarding the land — to give it to you as an inheritance through your observance of this precept.

ואתנה 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.

ואתנה ... וארבה אותך, you should not think that on account of the circumcision your future descendants will be fewer because your reproductive organ has become weakened by the removal of the foreskin. On the contrary, I will multiply your seed.
במאד מאד, an expression designed to express the unusual extent of what is about to happen. The word מאד always refers to some form of multiplicity.