John Gill, on Gen 17:24

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

“And Abraham was ninety years old and nine,.... See Gen 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 Gen 17:23; and Abraham might circumcise himself, as Ben Melech thinks. (u) Pirke Eliezer, c. 29.”

Imported from an open dataset — not yet checked against the printed edition.