וַיָּ֤מָל אַבְרָהָם֙ אֶת־יִצְחָ֣ק בְּנ֔וֹ בֶּן־שְׁמֹנַ֖ת יָמִ֑ים כַּאֲשֶׁ֛ר צִוָּ֥ה אֹת֖וֹ אֱלֹהִֽים׃
And Abraham circumcised his son Isaac when he was eight days old, as God had commanded him.
Targum Jonathan on Genesis
And Abraham circumcised Izhak his son, when the son of eight days, as the Lord had commanded him.