Washing the front and back passages during istinja'

Q: When performing istinja' for prayer, is it obligatory to wash both the front and back passages, or is washing only the front passage sufficient?

A: It is obligatory to wash the back and front passages if impurity, such as feces or urine, has come out of them. However, if nothing has come out of them, and the person has only passed wind, slept, touched his private parts without a barrier, or eaten camel meat, then wudu' is sufficient for him. Wudu' consists of washing the face and hands up to the elbows, wiping the head and ears, and washing the feet up to the ankles. Istinja' is not prescribed for him in this case, because no urine, feces, or anything equivalent to them has come out of him. If only urine has come out of him, then washing the tip of the penis of the urine is sufficient for him, and washing the back passage is not prescribed for him if nothing has come out of it. Then he performs wudu' for prayer, as mentioned earlier. The washing of the face includes rinsing the mouth and sniffing water into the nose.
And success is from Allah.