What was the description of the Prophet’s — may Allah’s peace and blessings be upon him — method of Istinja’ (cleaning oneself after urinating) with water, and has there been any mention in the Sunnah regarding the method of Istinja’, the quantity of water used, and how to purify one’s hands?

The Prophet, peace and blessings be upon him, used to forbid extravagance in the use of water and was economical in its use for purification (tahara) and cleansing after relieving oneself (istinja). He would perform ablution (wudu) with one mudd (a measure of volume). His guidance for istinja was to use the left hand to remove impurities and filth, and the right hand for purification and eating. After completing istinja, he would rub his hand on the ground or a wall to remove traces and unpleasant odors, which is similar to using soap today. Then he would perform his ablution for prayer, beginning by washing his hands three times before inserting them into the vessel.