Genesis 17:10
This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised. This is my covenant, which ye shall keep, between me and you and thy seed after thee; Every man child among you shall be circumcised.
This is my covenant to be kept between God and Abraham and his seed after him, that every male child among them shall be circumcised as its sign, token, and pledge. The cut, a circle cut in the flesh, meant that God had cut them out and separated them from all other nations and from idolaters as his special people and peculiar treasure, devoted to his service and accepted for himself. By receiving it they solemnly pledged to fulfill their part of the covenant by remaining separate and faithful and perfect and by obeying the law of God.
Keeping that covenant meant keeping the law of God as given to Adam after his fall, preserved by Noah, and observed by Abraham, and if man had kept that law there would have been no need for the ordinance of circumcision. That separateness especially forbade intermarriage and alliances and mixing with heathen peoples, lest nearness weaken reverence for God and his holy law. Such union would expose them to sinful practices and adoption of heathen practices, to rebellion against God and seduction into idolatry and becoming like the idolatrous nations around them, while keeping separate would remove that great temptation.
Because they mingled with the nations they lost in great measure their peculiar holy character, and to punish them God brought famine that forced them down into Egypt to preserve their lives. There their sojourn and bondage, through intercourse with idolaters and forced submission to the Egyptians and disposition to form alliances with the heathen and adopt their practices, still further corrupted the divine precepts. Yet God did not forsake them in Egypt because of his covenant with Abraham, but suffered them to be oppressed by the Egyptians so that in distress they would turn back to him, choose his righteous and merciful government, and obey his requirements.
If Abraham's descendants had kept the covenant pledged by circumcision, they would never have been seduced into idolatry, never have been allowed to go down into Egypt nor have had to suffer bondage there, and would have kept God's law in mind. Then there would have been no need for God to proclaim the Ten Commandments from Sinai and engrave them on tables of stone, nor to guard and expand them by the definite judgments and statutes spoken to Moses in the mount and written by Moses in a book. Those judgments and statutes are the principles of the Ten Commandments simplified and given definitely to draw erring man to obedience so they need not err.
Circumcision is the condition by which a child is entitled to the blessings of God's covenant with Israel, so neglect of this known requirement leaves the child without covenant title. Even yielding to a wife's persuasion does not excuse it, and in a chosen leader such neglect lessens the force of the divine precepts upon the people. On the way from Midian Moses was met by an angel in a threatening manner as if to destroy him at once because his youngest son was uncircumcised, and only when Zipporah herself performed the rite was Moses permitted to go on.
While living in neglect of known duty no one is secure and cannot be shielded by the angels of God, whose protection alone could preserve Moses in the great peril of his mission to Pharaoh. So in the time of trouble just before the coming of Christ the righteous will be preserved through the ministration of heavenly angels, but there will be no security for the transgressor of God's law. Angels cannot protect those disregarding even one divine precept.