What has been established concerning Tubba', who is mentioned in the Qur’an, and was he a monotheist or a disbeliever?

The Holy Quran mentions "Tubba‘" in two places, in the context of the destruction of his criminal people. Tubba‘ was one of the kings of Yemen, then he embraced Islam and worshipped Allah according to the law of Moses. The Prophet, peace and blessings be upon him, forbade us from reviling him because he was a righteous man. Ibn Kathir mentioned that "Tubba‘" was a title for kings, and his kingdom reached Samarkand. He passed through Medina and intended to fight its people, then he revered the Kaaba and clothed it, and invited the people of Yemen to Judaism, but they returned to idol worship after his death. It is mentioned that he was "Tubba‘ al-Awsat" As'ad Abu Karib, and he ruled for 326 years, and died seven hundred years before the Prophet Muhammad's mission, peace and blessings be upon him. It is mentioned that he saw a prophecy about the Prophet Muhammad, peace and blessings be upon him.