It is narrated from Sayyiduna al-Hasan bin Ali (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) performed ablution (wudu), he would leave some water over until he poured it over the place of his prostration.
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2726