Is bay’ah obligatory, or is it Sunnah?

Taking bay'ah, the pledge to a shaykh (also written bai'at, bay'at, baiat or bayt), is a Sunnah. The Beloved Prophet ﷺ took the pledge from the Companions on various occasions, and the Companions took the pledge at the occasions of the battles, to testify Allah, to be righteous, to obey in everything good or not to die except firmly upon Islam.

On the occasion of Hudaybiyyah, the pledge was taken from the Companions to be steadfast and to have fortitude in battle, and Allah approved of the pledge: "Indeed those who pledge allegiance to you, Muhammad ﷺ, they are actually pledging to Allah. The hand of Allah is over their hands." [Qur'an, al-Fath 48:10] The pledge was not only taken for steadfastness in war, though: there were various other occasions when it was taken from the Companions for matters other than war.

A hadith verifies the importance of bay'ah, where the Beloved Prophet ﷺ took a pledge from a group of his Companions and said, "Give me your pledge that you will not ascribe partners to Allah and that you will not steal." [Sahih al-Bukhari 18] Not only are there examples of a pledge for performing a good deed, but there are also examples of taking the pledge for forbiddance, as mentioned in this hadith. Therefore, bay'ah, or taking the pledge, is a Sunnah.

Bay'ah in Tasawwuf is a pledge to follow the Shariah rather than an ordinary pledge. Therefore, one must find someone who is fully adherent to the Shariah and capable of leading.

Mujaddid Alf Thani rahimahullah said: "This world is the ground for the Hereafter. His is a sad case who did not plant, but rather neglected his land, wasting away the seeds of his deeds. You should know that the land can be wasted away in two ways: Firstly, by not laying any seed at all or by sowing the wrong and rotten seeds. In comparison, this second wasting is more harmful than the first one. And, wrong and rotten seed consists in entering into bay'a (pledge) with an imperfect Peer. An imperfect peer suffers from greed and follows evil desires. He will pass these traits to his disciples. He himself is misguided and can only misguide others. In contrast, an accomplished Shaykh is like elixir, his sight is medicine and his talk is cure." [Imam Rabbani, Maktoob 23, vol. 1]