It is said that this man was Al-Bara' ibn Ma'rur al-Ansari. Furthermore, when one wishes to perform istinja, he should wipe from the area of the anus to the testicles three times, then shake the private part three times. When pouring water over his hand for istinja, he should say, "Praise be to Allah سبحانه وتعالى, who made water purifying and did not make it impure." He should pour on his private part twice the amount of water that was on it from urine; this is the minimum required. Then he should perform istinja for feces and wash until clean. The person performing istinja should pour water when the flow of urine has stopped. If someone prays and remembers afterward that he did not wash his private part, he must wash it and repeat his ablution and prayer. However, if he forgets to perform istinja after relieving himself and prays, he does not need to repeat the prayer. For feces, it is sufficient to perform istinja with stones, pottery, or soil (apart from water).
Commentary #8