80 Heb “he”; the referent (the Lord) has been specified in the translation for clarity.
81 Or “Therefore.” The particle אָז (’az) here is not introducing the next item in a series of events. It points back to the past (“at that time,” see Gen 4:26) or to a logical connection (“therefore, consequently”).
82 The Hebrew simply has לַמּוּלֹת (lammulot, “to the circumcision[s]”). The phrase explains that the saying was in reference to the act of circumcision. Some scholars speculate that there was a ritual prior to marriage from which this event and its meaning derived. But it appears rather that if there was some ancient ritual, it would have had to come from this event. The difficulty is that the son is circumcised, not Moses, making the comparative mythological view untenable. Moses had apparently not circumcised Eliezer. Since Moses was taking his family with him, God had to make sure the sign of the covenant was kept. It may be that here Moses sent them all back to Jethro (18:2) because of the difficulties that lay ahead.

In other versions

So he let him alone. It was then that she said, “A bridegroom of blood,” because of the circumcision.

So the Lord let him alone. (At that time she said “bridegroom of blood,” referring to circumcision.)

So he let him alone. At that time she said, “You are a bridegroom of blood,” referring to the circumcision.

(When she said “a bridegroom of blood,” she was referring to the circumcision.) After that, the Lord left him alone.

And he left him alone. At that time she said, “A bridegroom of blood,” because of the circumcision.

So he let him go: then she said, A bloody husband thou art, because of the circumcision.

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