Growing a beard is an extremely emphasised and encouraged way (Sunnah) of the Messenger of Allah (Allah bless him & give him peace), and held by the Muslim scholars to be necessary (wajib) for a man.
1) Sayyiduna Abd Allah ibn Umar (Allah be pleased with him) narrates that the Messenger of Allah (Allah bless him & give him peace) said: “Trim (your) moustaches and lengthen/grow (your) beards.” (Sahih al-Bukhari & Sahih Muslim)
2) Sayyiduna Abu Hurayra (Allah be pleased with him) narrates that the Messenger of Allah (Allah bless him & give him peace) said: “Cut off moustaches, leave beards and do otherwise than the fire worshippers.” (Sahih Muslim, no. 260)
3) Sayyiduna Anas ibn Malik (Allah be pleased with him) narrates that the Messenger of Allah (Allah bless him & give him peace) said: “Trim moustaches, lengthen/leave beards and do not imitate the Jews.” (Tahawi, Sharh Ma’ani al-Athar, 4/230)
4) Sayyiduna Abd Allah ibn Umar (Allah be pleased with him) narrates that the Messenger of Allah (Allah bless him & give him peace) ordered the trimming/clipping of moustaches and the leaving of the beards.” (Sahih Muslim, no. 1/222)
The great Hadith master, Imam al-Nawawi (Allah have mercy on him) states in his renowned commentary of Sahih Muslim:
The words: A’fu, Awfu. Arkhu, Arju and Waffiru have all been used; the meaning of all of which is to leave the beard as it is.” (Sharh Sahih Muslim, 3/151)
A small and best booklet about keeping beard (Sunnah) as per sayings of Prophet Muhammad Salaih Allah WaSalam
By Shaikh-ul-Hadees Molana Zakriyah Kandhlvi rahmatullah
in Urdu language.