What is the ruling on a Muslim man shaving his beard? And is it considered a major sin?

Shaving the beard is unlawful (haram), due to what is narrated in the authentic hadiths regarding the command to let it grow and lengthen it, and to differ from the polytheists and Magians, and what these hadiths necessitate of prohibition according to the Hanbalis. Ibn Hazm narrated a consensus on the obligation of letting the beard grow.

The Qur’an, Sunnah, and consensus have indicated the unlawfulness of imitating disbelievers, and shaving the beard is a form of imitating them. It is not a grave sin except with persistence. Repentance is obligatory for all sins.