Abraham circumcised his son Isaac when he was eight days old: Abraham follows the instructions given to him by God in 17.11-14. For discussion of circumcised see 17.10. For eight days old see 17.12.

As God had commanded him: for a similar expression see 17.23. Looking back to chapter 17 we see that some translations express this as “Abraham kept the promise [covenant] he had made with God, and circumcised Isaac.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .