It is not obligatory for him; because the mind is a condition for its obligation, and he is not among those addressed and obligated; as Ali, may Allah be pleased with him, narrated that the Prophet, peace be upon him, said: ((The pen is lifted from three: from the child 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 Abi Ya'la 1: 440. See: Maraqi al-Falah p. 173.