The Pulpit Commentary - Genesis 17:1
And when Abram was ninety years old and nine —consequently an interval of thirteen years had elapsed since the birth of Ishmael; the long delay on the part of God being probably designed as chastisement for Abram's second nuptials (Calvin), and at least corresponding with Abram's undue haste (Lange)— the Lord appeared to Abram— lest he should regard Ishmael's birth as a complete fulfillment of the promise (Menochius), and be satisfied with Hagar's child as the expected seed (Calvin)— ... read more
John Calvin's Commentary on the Bible - Genesis 17:23
Verse 23 23.And Abraham took Ishmael Moses now commends the obedience of Abraham because he circumcised the whole of his family as he had been commanded. For he must, of necessity, have been entirely devoted to God, since he did not hesitate to inflict upon himself a wound attended with acute pain, and not without danger of life. To this may be added the circumstance of the time; namely, that he does not defer the work to another day, but immediately obeys the Divine mandate. There is, however,... read more