창세기 17:21의 주석

למועד הזה "at this time." (anniversary). We do not know precisely on what date G'd had granted Avraham this prophetic vision.

ואת בריתי אקים את יצחק, “and My covenant I will establish with Yitzchok;” the word אקים is to be understood as an acrostic from the phrase: אשר קידש ידיד מבטן, a phrase recited after every circumcision, meaning: “who is well beloved already when he emerges from the womb.”