Exodus 4:24, 25, 26

One night while Moses was in camp, the LORD was about to kill him.

But Zipporah circumcised her son with a flint knife. She touched his legs with the skin she had cut off and said, “My dear son, this blood will protect you.”

So the LORD did not harm Moses. Then Zipporah said, “Yes, my dear, you are safe because of this circumcision.”