Musannaf Ibn Abi Shayba 3:6459

Al-Dahhak ibn Makhlad narrated to us, from Uthman ibn al-Aswad, who said: Mujahid saw me while I was sprinkling water on a place on a roof of ours where we pray. He said: "Do not sprinkle water, for sprinkling does not increase it except in evil (i.e., making it worse). Rather, look at the place where you intend to prostrate, and blow upon it."