2 Kings 3:20-23
English Standard Version
21When all the Moabites heard that the kings had come up to fight against them, all who were able to put on armor, from the youngest to the oldest, were called out and were drawn up at the border.
22And when they rose early in the morning and the sun shone on the water, the Moabites saw the water opposite them as red as blood.
23And they said, "This is blood; the kings have surely fought together and struck one another down. Now then, Moab, to the spoil!"