The beard is the Sunnah of all the Prophets and also the Sunnah of the Messenger of Allahﷺ.
The Messenger of Allah ﷺ has emphasised on the lengthening of the beard so much, to the extent it is necessary (wajib) to keep a beard. Many people think that the beard is only a Sunnah, however, whatever is Fardh, Wajib, Sunnah and Mustahab are all Sunnah too, but fall into different categories depending on the emphasis in the Qur'an and hadith. Hence, the beard falls into the category of Wajib due to its emphasis laid in the hadith and the practises of the companions.
reference : www.zikr.co.uk
credit image : Angelina Litvin
