I say, and with God's success: First: Puberty: Prayer is not obligatory on a minor; as there is no address to him. Second: Reason: Prayer is not obligatory on the insane; because he is not accountable; as Ali, may God be pleased with him, said: "The pen is lifted from three: from the boy until he reaches puberty, from the sleeper until he wakes up, and from the insane until he recovers," in Sunan Abu Dawood 4: 140, and Sunan Al-Nasa'i Al-Kubra 4: 324, and Musnad Al-Tayalisi 1: 15, and Musnad Abu Ya'la 1: 440. Third: Islam: Prayer is not obligatory on the disbeliever; because Islam is a condition for addressing the branches of Sharia, and the disbeliever is not among the people of Islam. See: Maraqi Al-Falah p. 173, and God knows best.