In Genesis 4:15, the Bible says that God "marked" Cain "lest anyone finding him should kill him." The Bible is not clear as to what this "mark" was. In the Spirit-Filled Life Bible, of which Pastor Hayford served as General Editor, the study notes under this passage say:

"The mark on Cain is unidentifiable, since his descendants perished in the Flood. The mark was not a stigma, but rather a protection for Cain and shows God’s incredible love for even impenitent sinners."

Ezekiel 9:4 says that a "mark" was put on the foreheads of the men. The study notes say:

"Put a mark: The Hebrew word for "mark" is taw, the final letter of the Hebrew alphabet, which in the ancient script looked like an "X" or a cross. This mark, placed by a seventh warrior angel "clothed with linen" (v. 3), was for protection (see Rev. 7:3) and symbolized that God would spare the righteous remnant."