Exodus 4:24, 25, 26

On the way to Egypt, Moses stopped at a place to spend the night. The LORD met Moses at that place and tried to kill him.

But Zipporah took a flint knife and circumcised her son. She took the skin and touched his feet. Then she said to Moses, “You are a bridegroom of blood to me.”

Zipporah said this because she had to circumcise her son. So God let Moses live.