Берешит 17:19 Комментарий: Rashi, Chizkuni, Ramban & Kli Yakar

אבל VERILY — This word implies confirmation of a statement, just as (Genesis 42:21) “Verily (אבל) we are guilty”, and (2 Kings 4:14) “Verily (אבל) she has no son”.

והקימותי את בריתי אתו, “I will maintain My covenant (the promise contained therein) with him.” G-d means that Yitzchok will be the first person to be circumcised on the eighth day of his life.

‘AVAL’ SARAH THY WIFE. This is like the verse, “Aval” she has no son,⁴⁵⁷II Kings 4:14. the word aval meaning “only.” He thus said: “Only the son of whom I informed you, your wife Sarah will give birth to, and with him will I establish My covenant forever and with his seed after him; and Ishmael I will bless by making his children numerous, but this will not be because of My covenant with him.”