What should a Muslim do concerning the division of Muslims into sects and parties, and their mutual excommunication, and what do you advise him?

The division of Muslims into multiple sects is a divine decree. Ahl al-Sunnah wa al-Jama'ah are those whom Allah has protected from disagreement regarding the fundamentals and universals of religion. They are the people of truth, established upon the Qur'an, the Sunnah, and the methodology of the Prophet (peace be upon him) and his Companions and the Tabi'in (successors). This is in contrast to the Sufis, who innovated in religion. Some of their innovations are considered acts of disbelief, such as those of Ibn Arabi and Al-Hallaj, while some of their sects involve innovations that are considered acts of transgression. It should be noted that some individuals associated with Sufism may adhere to the Sunnah and be free from innovation, such as Qadi Iyad and Ma'ruf al-Karkhi; these are among the imams of Ahl al-Sunnah. It is advised to adhere to the methodology of the Prophet (peace be upon him) and his Companions in belief and action, and to accept the truth and stay away from error.