A missing dimension is much Bible study is an understanding of types or shadows, and how they work. The sign of circumcision as given to Abraham can be a useful study.

“This is my covenant, which you shall keep, between me and you and your seed after you. Every male among you shall be circumcised.”
Gen 17:10 WEB

Abraham, then 99 years old, and all his house, were immediately circumcised, Gen 17:22-24. Also was the command that if any were not circumcised, they were to be “cut off,” Gen 17:14. And “cut off” meant to be put to death, as in Gen 9:11 and many other passages.

So Circumcision became central to
God’s covenants.

So when Moses was called by the Lord the lead Israel out of Egyptian bondage, it was natural that circumcision was an issue. It is unclear what all was going on in the latter part of Exodus 4. If I were guessing, I would say that Moses knew that his sons should be circumcised, but that his wife Zipporah had prevented that from happening! Perhaps she just felt that was nothing that should be done to child: cruel, hurtful, although commanded. So it says,

“24 It happened on the way at a lodging place, that Yahweh met him and wanted to kill him. 25 Then Zipporah took a flint, and cut off the foreskin of her son, and cast it at his feet; and she said, “Surely you are a bridegroom of blood to me.” 26 So he let him alone. Then she said, “You are a bridegroom of blood,” because of the circumcision.”
Ex 4:24-26 WEB

A strange passage no doubt. And how did Yahweh appear to Moses? John, like others, tells us,

“No one has seen God at any time. The one and only Son, who is in the bosom of the Father, he has declared him.”
Jn 1:18 WEB

So was this an angel called the “angel of Yahweh” as in Gen 16:7? Or is it like Exodus 3 where it says,

“The angel of Yahweh appeared to him in a flame of fire out of the midst of a bush. …”
Gen 3:2 WEB

And then Yahweh spoke from the burning bush, and it says,

“Yahweh said, “I have surely seen the affliction of my people …”
Ex 3:7 WEB

And when Moses answered it says,

“Moses said to God, “Who am I, that I should go to Pharaoh, …”
Ex 3:11 WEB

Many mysteries (in the modern sense) are here. Still it is clear that circumcision was required. Holiness was to be to the extent of cutting off some parts of yourself, even of your private parts, if that was necessary to cleanse yourself before God! So circumcision became a requirement in Moses law, Lev 12:1-3.

But some other things were there.

So Moses said,

“Circumcise therefore the foreskin of your heart, and be no more stiff-necked.”
Deut 10:16 WEB

Thus indicating physical circumcision was symbolic of something even more important. Inner cleansing!

WEB is the World English Bible, a copyright free revision
of the original ASV American Standard Version 1901