“Abraham called the name of his son who was born to him, whom Sarah bore to him, Isaac” (Genesis 21:3). “Abraham called the name of his son…Isaac [Yitzḥak]” – a portion has emerged [yatza ḥok] to the world, [meaning that] a gift has been given to the world.22Ḥok here refers to a portion given as a gift (see Genesis 47:22). A righteous person is a gift to the world, as the merit of his good deeds provides all mankind with sustenance.
Rabbi Yitzḥak Ḥipushit said: Yod is ten – corresponding to the Ten Commandments; tzadi is ninety – “shall a ninety-year-old woman give birth?” (Genesis 17:17); kof is a hundred – “to one who is one hundred years old” (Genesis 17:17); ḥet [is eight] – corresponding to circumcision, that was given to be performed on the eighth day.23The letters yod, tzadi, ḥet, and kof spell Yitzḥak – Isaac. “Abraham circumcised Isaac his son when he was eight days old, as God had commanded him” (Genesis 21:4).
“Abraham circumcised Isaac…[when he was eight days old, as God had commanded him].” That is what is written: “One who is eight days old shall be circumcised among you, every male throughout your generations” (Genesis 17:12).