According to Merriam-Webster English Dictionary, “circumcision” is
“the cutting off of the foreskin of males that is practiced as a religious rite by Jews and Muslims and by others as a social custom or for potential health benefits (such as improved hygiene)”
Though Jews practice this surgery as a religious rite, its health benefits are also intended. For example, Leviticus 11-19, or “the Purity Code,” in which many hygienic practices are listed as God’s commandments, includes regulations for women in the state of maternity (Lev 12), and the rules are to prohibit touching them to protect the women and their community from the spread of unknown illnesses–they did not have the knowledge of the microorganism, so they tried to be careful at any circumstances. Interestingly, the law of circumcision is mentioned as one of the regulations in Lev 12 for women in the state of maternity. That means circumcision is not merely a religious rite but a hygienic practice for Jews too.
However, unlike other regulations mentioned in the Purity Code, the Hebrew Bible treats the law of circumcision very specially as a religious rite. Circumcision is not just another purity regulation for Jews.
Its importance is perhaps most dramatically addressed in Exodus 4, the event of “bridegroom of blood.” In the passage, Moses, called by God, departed his journey with his family to Egypt. Then, one night, the Lord suddenly appeared and tried to kill Moses. So Moses’s wife Zipporah quickly grabbed a flint and cut off the son’s foreskin. We do not know how she knew the event’s cause was the lack of his son’s circumcision. Anyway, she circumcised his son, and the Lord left Moses alone. So Zipporah called him “a bridegroom of blood by circumcision.” It is extremely confusing why the Lord tried to kill him after the Lord called him to save Israel from Egypt. Maybe it is because circumcision is that important.
Nevertheless, it is still hard to understand why God tried to kill him, even though we can understand that circumcision is important. The key to this mystery is in Ex 4:22-23.
22 Then you shall say to Pharaoh, ‘Thus says the LORD: Israel is my firstborn son. 23 I said to you, “Let my son go that he may worship me.” But you refused to let him go; now I will kill your firstborn son.'”(NRSV)
The text above indicates that Israel is God’s firstborn son. They became God’s people after God made a covenant of circumcision with Abraham. God said if they do not cut off their foreskins, they will be cut off from God’s people. To summarize, Israel became God’s people as they practice circumcision, and God’s people Israel is also called God’s firstborn son. Egypt, however, persecuted God’s firstborn son and restrained them. So God is going to repay the firstborn sons of Egypt the price of the persecution of God’s firstborn son who got the sign of circumcision. Therefore, Moses’s journey is not a peaceful picnic type of journey but a way to kill all the firstborn sons in Egypt. But Moses did not perform circumcision on his son. In other words, Moses’s son is merely Moses’s firstborn son but not God’s firstborn son. If he arrives in Egypt, he is not different from those who do not have the sign of circumcision, the mark of God’s firstborn son.
You may wonder how Moses had not circumcised his own son. He was on his way to kill those who did not have the mark of God’s people, but he ironically did not give his son the mark. His mistake should not have happened, and it cannot be tolerated. So God tried to kill Moses as he did not comprehend the significance of his journey, the way to separate life and death, God’s circumcised firstborn sons and Egypt’s uncircumcised ones. Exodus 4 shows us an event that explains the graveness of God’s judgment on the firstborn sons of Egypt for God’s own firstborn son Israel. Circumcision is that important for Jews.