The Prophet ﷺ said, “Do not pluck out grey hair, for it is the light of the Muslim.” ⦗fair hadith⦘
There is no difference whether it is plucked from the beard or from the head. Anas (may Allah be pleased with him) said, “It is disliked for a man to pluck a white hair from his head or his beard.” ⦗Narrated by Muslim⦘
As for the one who shaves his beard, he has taken exception to black hair—much less to the white hair that is the Muslim’s light.
It is reported that ʿUmar (may Allah be pleased with him) and Ibn Abī Yaʿlā, the judge of Madinah, rejected the testimony of anyone who plucked out his beard.
Al-Ghazālī and al-Nawawī—may Allah have mercy on them—said: “Plucking the beard when it first begins to grow is an imitation of the murd (1) and is among the gravely reprehensible acts.”
Letting the beard grow is a Prophetic sunnah
Allah, exalted is He, says: “Indeed, in the Messenger of Allah you have an excellent example.” ⦗Al-Ahzab 33:21⦘