Leviticus 27:32

Passeth under the rod. Rabbinical writers give the following explanation: When a man was to give the tithe of his sheep or calves to God, he shut up the whole flock in one fold, in which there was a narrow door capable of letting out one animal at a time. The owner about to give the tenth to the Lord stood by the door with a rod in his hand, the end of which was dipped in vermilion or red ocher. The mothers of these lambs or calves stood without. When the door was opened the young ones ran out to join their mothers, and as they passed out, the owner stood with his rod and touched every tenth one, coloring it. Whether poor or lean, perfect or blemished, it was re-received as the legitimate tithe.