That very day, the same expression as in verse 23, refers to the day Abraham, Ishmael, and the other males were circumcised. This verse has the effect of emphasizing the prompt obedience of Abraham. See Good News Translation for an adequate model.

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 .