What is the ruling concerning water that has mixed with a drop of a man's prostatic fluid or semen; is it pure or impure?

Scholars have differed concerning the ruling on semen. It is considered pure by some, such as the Hanbalis and Shafi'is, and impure by the Malikis and Hanafis. The preponderant opinion, due to the strength of its evidences, is that it is pure. According to the view of its purity, the presence of some of it in water without altering it does not affect the water's usability. If it alters the water, then semen itself is pure, but there is a difference of opinion regarding whether it can purify other things.