Sheikh Muhammad al-Manî`î, professor at Umm al-Qurâ University
After a man finishes urinating, he has to make sure that the stream of urine has stopped. Then he must wash his penis and be done with it.
He should not entertain any suspicions about the possibility of urine.
There is an old saying about this matter that the urine in a man’s penis is like milk in an udder; it will keep coming up if it is squeezed, and it will stop once it is left alone.
Source: Islam Today