To which people did God send the Prophet Shu'ayb, peace be upon him?

Allah sent Shu'ayb (peace be upon him) to the People of Al-Aykah, who were the people of Madyan. Allah says: "And to Madyan [We sent] their brother Shu'ayb" (Hud: 84), and He says: "The companions of the Aika [i.e., the people of Madyan] denied the messengers, when Shu'ayb said to them, 'Will you not fear Allah?'" (Ash-Shu'ara: 177). The reason "their brother" was not mentioned in the second verse is because they were attributed to the worship of Al-Aykah, which is a tree. Thus, the relationship of brotherhood was severed due to the meaning to which they were attributed, even though he was their brother by lineage. The correct view is that they were one nation.