God tries to kill Moses because his son had not yet been circumcised. Luckily for Moses, his wife Zipporah took a sharp stone, and cut off the foreskin of her son, and touched Moses's feet with it. So God lets him go.
The Bible: "At a lodging place on the way, the Lord met Moses and was about to kill him. But Zipporah took a flint knife, cut off her son’s foreskin and touched Moses’ feet with it. ‘Surely you are a bridegroom of blood to me,’ she said. So the Lord let him alone. (At that time she said ‘bridegroom of blood,’ referring to circumcision.)"
- Exodus 4:24-26
Quote Source: The Bible