"Twice a father of a multitude" in the passage, which refers to Abraham, is taken into account for Isaac. And "arbah" (meaning "four") has the same numerical value as Isaac in Hebrew numerology (gematria).

"הפר" in two senses in the text. On one hand, it means "break," and on the other hand, it means "violate his commandment." The Midrash explains it as drawing a comparison between the breaking of the foreskin during circumcision to the breaking of an animal's neck. Just as the neck is broken during the sacrifice of an animal, so too does one violate the commandment of circumcision by not circumcising.

"I will establish my covenant with Isaac" - "אקים" can be interpreted as a hint that God sanctified His beloved friend (Isaac) from the womb.