Exodus 4:26

Jehovah had been ready to kill Moses, but now lets him go after Zipporah circumcises their son. On an internal level, this shows that with the internal evil of the people of Israel exposed and acknowledged, they could be used to represent spiritual things.

This, of course, actually happened as Moses received rules from God and enforced them on the Children of Israel, despite their many wanderings. And we have those rules in the form of Bible, which – when we understand it's true meaning – is completely relevant to our modern lives. So we can see that the promise of Zipporah benefits us now.

By again calling Moses a "bridegroom of blood" Zipporah is acknowledging the hatred and violence the people of Israel have at heart toward all that is loving and true. Despite that, mentioning the circumcision again means that it can be an external form of worship that represents purification from things that are evil and false.