Because of the morning sun, which meeting with the vapours that arose from the earth, and shining through them upon the water, gave it a reddish tincture. God also so ordered things, that their senses and fancies were disturbed, or the air so disposed, that it might seem of this colour. And they might more easily mistake this for blood, because they knew that that ground was generally dry, and without any trenches or streams of water, now especially in this dry season, there being no noise of wind and rain, 2 Kings 3:17. And they might justly think that the three kings being divided in their religion and interests, and discontented for want of water, might fall into dissensions, and heats, and mutual slaughters, of which they had a late example, 2 Chronicles 20:22,23.
Related Commentaries of 2 Kings 3:22
2 Kings 3:22
22 And they rose up early in the morning, and the sun shone upon the water, and the Moabites saw the water on the other side as red as blood: