And Abraham was ninety years old and nine,.... See Genesis 17:1. This circumstance of his age is observed the more to commend his faith and obedience, that though he was an old man, he did not consider his age, or make that an objection; that he was unable to bear the pain, or it would be shameful for a man of his years to be uncovered before his servants:

when he was circumcised in the flesh of his foreskin; who circumcised him is not said, very probably Eliezer his head servant: the Jews, who affect to know everything, say (u), that he sent for Shem, the son of Noah, who circumcised him and his son Ishmael; but it is most likely that Ishmael was circumcised by Abraham himself, as seems from Genesis 17:23; and Abraham might circumcise himself, as Ben Melech thinks.

(u) Pirke Eliezer, c. 29.

And Abraham was ninety years old and nine, when he was circumcised in the flesh of his foreskin.

17:23-27 Abraham and all his family were circumcised; so receiving the token of the covenant, and distinguishing themselves from other families that had no part nor lot in the matter. It was an implicit obedience; he did as God said unto him, and did not ask why or wherefore. He did it because God bade him. It was a speedy obedience; in the self-same day. Sincere obedience makes no delay. Not only the doctrines of revelation, but the seals of God's covenant, remind us that we are guilty, polluted sinners. They show us our need of the blood of atonement; they point to the promised Saviour, and teach us to exercise faith in him. They show us that without regeneration, and sanctification by his Spirit, and the mortification of our corrupt and carnal inclinations, we cannot be in covenant with God. But let us remember that the true circumcision is that of the heart, by the Spirit, Ro 2:28,29. Both under the old and new dispensation, many have had the outward profession, and the outward seal, who were never sealed by the Holy Spirit of promise.