Abraham was ninety-nine years old when he was circumcised: verses 24 and 25 state the age of Abraham and Ishmael when they were circumcised. Translators may keep these two verses separate or join them. Bible en français courant joins them in the following manner: “Abraham was ninety-nine years old and his son Ishmael thirteen when they were circumcised.” In languages in which the passive cannot be used here, it will be necessary to form an active construction. It may be necessary, for example, to use an impersonal subject, “They circumcised Abraham when he was….” (See the discussion at verse 10.)

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 .