The fact that man was created from worthless water is a fact that is stated in the Qur'an and is obvious from experience. Allah, may He be exalted, says (interpretation of the meaning):
Did We not create you from a worthless water (semen, etc.)?
So let man see from what he is created!
He is created from a water gushing forth
This gushing, worthless water is maniy (semen), and according to the more correct of the two scholarly opinions it is taahir (pure). Its purity is indicated by a great deal of evidence, including the following:
The report narrated by Muslim (288) from Aa'ishah (may Allah be pleased with her) who said: I remember scratching it (maniy) from the garment of the Messenger of Allah (blessings and peace of Allah be upon) thoroughly, then he prayed in it. It is well-known that scratching is not sufficient to remove impurity, which indicates that it is pure.
Further proof may be found in the fact that this water is the origin of the sincere slaves of Allah, such as the Prophets, siddeeqs, martyrs and righteous people, and the wisdom of Allah, may He be exalted, dictates that the origin of these righteous people cannot be impure.
End quote from ash-Sharh al-Mumti, 1/388
The scholars of the Standing Committee for Issuing Fatwas were asked: If maniy gets onto clothes, does it make them impure?
They replied: The basic principle concerning it is that it is pure and we do not know of any evidence to suggest that it is impure. End quote.
Fataawa al-Lajnah ad-Daa'imah, 6/416
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
With regard to maniy, the correct view is that it is pure, as is the view of ash-Shaafai and Ahmad, according to the well-known report from him. It was also said that it is impure, but it is sufficient to scratch it, as is the view of Abu Haneefah and Ahmad, according to the other report.
And it was said that it must be washed, as is the view of Maalik.
The first view is the correct one, because it is well-known that the Sahaabah experienced wet dreams at the time of the Prophet (blessings and peace of Allah be upon him) and that maniy would get onto the body and clothes of one of them, and this is something that affects everyone. If it were impure, then it would have been obligatory for the Prophet (blessings and peace of Allah be upon him) to instruct them to remove that from their bodies and clothes, as he instructed them to clean themselves after relieving themselves, and as he instructed the menstruating woman to wash the menstrual blood from her garment. In fact, the issue of getting maniy on one's body or clothes is far more common than the issue of menstrual blood getting onto the woman's garment. It is well-known that no one narrated that the Prophet (blessings and peace of Allah be upon him) instructed any of the Sahaabah to wash maniy from his body or clothes; thus it is known for certain that this was not obligatory for them, and this is definitive to anyone who examines the matter.
End quote from Majmoo al-Fataawa, 21/604, 605
And Allah knows best.
Reproduced from Islam QA