Shu'bah, the freed slave of Sayyiduna Ibn Abbas (may Allah be pleased with them both), narrates that when Sayyiduna Ibn Abbas (may Allah be pleased with them both) performed the ritual bath (ghusl) for major impurity, he would pour water with his right hand onto his left hand seven times. Then he asked: O Shu'bah, how many times did you pour water on my hands? I said: I do not know. He said: May you have no mother! Why did you not know? Then he performed ablution (wudu) as for the prayer, then poured water over himself, then said: "This is how the Messenger of Allah (peace and blessings be upon him) used to purify himself."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12169