"Isaac's Circumcision", Regensburg Pentateuch, c1300
According to the Genesis 17:10–14) God commanded the Biblical patriarch Abraham to be circumcised, an act to be followed by his descendants:
10 This is My covenant, which ye shall keep, between Me and you and thy seed after thee: every male among you shall be circumcised. 11 And ye shall be circumcised in the flesh of your foreskin; and it shall be a token of a covenant betwixt Me and you. 12 And he that is eight days old shall be circumcised among you, every male throughout your generations, he that is born in the house, or bought with money of any foreigner, that is not of thy seed. 13 He that is born in thy house, and he that is bought with thy money, must needs be circumcised; and My covenant shall be in your flesh for an everlasting covenant. 14 And the uncircumcised male who is not circumcised in the flesh of his foreskin, that soul shall be cut off from his people; he hath broken My covenant.
Also, Leviticus 12:3 provides: "And in the eighth day the flesh of his foreskin shall be circumcised."
According to the Hebrew Bible, it was "a reproach" for an Israelite to be uncircumcised (Joshua 5:9.) The term arelim ("uncircumcised" [plural]) is used opprobriously, denoting the Philistines and other non-Israelites (I Samuel 14:6, 31:4; II Samuel 1:20) and used in conjunction with tameh (unpure) for heathen (Isaiah 52:1). The word arel ("uncircumcised" [singular]) is also employed for "impermeable" (Leviticus 26:41, "their uncircumcised hearts"; compare Jeremiah 9:25; Ezekiel 44:7, 9); it is also applied to the first three years' fruit of a tree, which is forbidden (Leviticus 19:23).
However, the Israelites born in the wilderness after the Exodus from Egypt were not circumcised. Joshua 5:2–9, explains, "all the people that came out" of Egypt were circumcised, but those "born in the wilderness" were not. Therefore, Joshua, before the celebration of the Passover, had them circumcised at Gilgal specifically before they entered Canaan. Abraham, too, was circumcised when he moved into Canaan.
The prophetic tradition emphasizes that God expects people to be good as well as pious, and that non-Jews will be judged based on their ethical behavior, see Noahide Law. Thus, Jeremiah 9:25–26 says that circumcised and uncircumcised will be punished alike by the Lord; for "all the nations are uncircumcised, and all the house of Israel are uncircumcised in heart."
The penalty of non-observance is Genesis 17:1–14. Conversion to Judaism for non-Israelites in Biblical times necessitated circumcision, otherwise one could not partake in the Exodus 12:48). Today, as in the time of Abraham, it is required of converts in Orthodox, Conservative and Genesis 34:14–16).
As found in Genesis 17:1–14, brit milah is considered to be so important that should the eighth day fall on the Sabbath, actions that would normally be forbidden because of the sanctity of the day are permitted in order to fulfill the requirement to circumcise. The Talmud, when discussing the importance of Milah, compares it to being equal to all other mitzvot (commandments) based on the gematria for brit of 612 (Tractate Nedarim 32a).
Covenants in ancient times were sometimes sealed by severing an animal, with the implication that the party who breaks the covenant will suffer a similar fate. In Hebrew, the verb meaning "to seal a covenant" translates literally as "to cut". It is presumed by Jewish scholars that the removal of the foreskin symbolically represents such a sealing of the covenant.
Due to Jesus having undertaken this ceremony as a Jewish child, memory of this tradition has been preserved in traditional Christian churches according to the Gospel of Luke. The Feast of the Circumcision of Christ is kept as a feast eight days after Nativity in a number of churches including the Eastern Orthodox Church, Catholic Church, Lutheran and some Anglican Communion churches. In Orthodox Christian tradition, children are officially named on the eighth day after birth with special naming prayers.
Significantly, the tradition of baptism universally replaced circumcision among Christians as the primary rite of passage as found in Paul's Epistle to the Colossians and in Acts of the Apostles.