To Shave One's Moustache

Question :

I request you to mention the Hadiths in which the Messenger of Allah said that whoever shaves his beard is a Fasiq. And is it permissible to completely shave the moustache?

Answer:

Shaving the beard is forbidden and the one who does so is a Fasią, because of his violation of the Hadiths which order it to be grown. The Permanent Committee for Scientific Researches and Religious Verdicts has previously answered a question similar to this one, giving the following ruling:
"Shaving the beard is forbidden according to what has beenbnarrated by Al-Bukhari, Muslim, Ahmad and others, on the authority of Ibn 'Umar, may Allah be pleased with him, from the Prophet ﷺ who said:
"Be different from the polytheists, and grow your beards and shorten your moustaches."

And according to what has been narrated by Muslim and Ahmad, on the authority of Abu Hurairah, may Allah be pleased with him, from the Prophet ﷺ, who said :
"Pare your moustaches and leave your beards, and differ from the Zoroastrians."

Continually shaving the beard is a major sin, therefore the shaver must be advised and reproved, especially if he is in a religious guidance center.

As for shaving the moustache, it has not been authentically reported from the Messenger of Allah, nor from his Companions, as far as we are aware. What has been confirmed from them is that they used to encourage people to clip and trim it. The Committee has issued a ruling regarding this issue; its number is 1954.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 8 Pages 245-246