Albert Barnes Commentary Exodus 4:25

"Then Zipporah took a flint, and cut off the foreskin of her son, and cast it at his feet; and she said, Surely a bridegroom of blood art thou to me." — Exodus 4:25 (ASV)

Sharp stone - Not “knife,” as in the margin. Zipporah used a piece of flint, in accordance with the usage of the patriarchs. The Egyptians never used bronze or steel in the preparation of mummies because stone was regarded as a purer and more sacred material than metal.

Cast it at his feet - Showing at once her abhorrence of the rite, and her feeling that by it she had saved her husband’s life.

A bloody husband - Literally, “a husband of blood,” or “bloods.” The meaning is: The marriage bond between us is now sealed by blood. By performing the rite, Zipporah had recovered her husband; his life was purchased for her by the blood of her child.