Exodus 4:25

Then Zipporah took a sharp stone, a stone knife, and cut off the foreskin of her son, and cast it at his feet, laid it down so that it touched the feet of Moses, and said, Surely a bloody husband art thou to me. The entire incident seems to have been a source of great displeasure to Zipporah, and her words indicate that she considered her husband regained by the blood of her child.