הלכה אויף בראשית 17:13

The master is under an obligation to circumcise his male slaves, whether at birth they were his property or whether they had been acquired from a non-Israelite. There is a distinction however between these cases. A slave born in an Israelite's home is circumcised on the eighth day after birth; the slave bought with money, on the day that he is bought. Even if he was born on the day he was bought, he is circumcised on the same day.

Mark how strictly the observance of Circumcision is to be regarded. Moses, although he was on a journey did not receive indulgence a single hour for neglecting this duty. In connection with all the precepts of the Torah, three covenants were made with Israel; as it is said "These are the words of the covenant which the Lord commanded … beside the covenant which He made with them in Horeb" (Deut. 28:69). And in the next section it is said "Ye are standing this day all of you before the Lord your God … that thou shouldst enter into the covenant of the Lord thy God" (Deut. 29:9-11). Three covenants are here mentioned. But in connection with Circumcision, thirteen covenants were made with our ancestor Abraham: "And I will make My covenant between Me and thee" (Gen. 17:2); "As for me. behold, My covenant is with thee" (ib. 17:4); "And I will establish My covenant between Me and thee" (ib. 17:7); "for an everlasting covenant" (ib. 17:7); "And as for thee, thou shalt keep My covenant" (ib. 17:9); "This is My covenant which you shall keep" (ib. 17:10) "And it shall be a token of a covenant" (ib. 17:11); "And My covenant shall be in your flesh" (ib. 17:13); "for an everlasting covenant" (ib. 17:13); "he hath broken my covenant" (ib. 17:14); "And I will establish My covenant with him" (ib. 17:19); "for an everlasting covenant" (ib. 17:19); "But My covenant I will establish with Isaac" (ib. 17:21).