His prayer was valid but disliked due to prohibition; as narrated by 'Uqbah ibn 'Amir al-Juhani (may Allah be pleased with him) who said: "There are three times when the Messenger of Allah (peace be upon him) forbade us to pray in them or to bury our dead: when the sun rises until it is fully up, when the sun is at its zenith until it moves, and when the sun is setting until it has completely set," in Sahih Muslim 1: 568, Musnad al-Mustadrak 2: 424, Sahih Ibn Hibban 3: 348, Sunan al-Tirmidhi 3: 348, and Sunan Abu Dawood 3: 208. And from Ibn Abbas (may Allah be pleased with both of them) who said: "Witnesses whom I trust and the most trusted among them is 'Umar, that the Prophet (peace be upon him) forbade praying after the dawn prayer until the sun rises and after the 'Asr prayer until the sun sets," in Sahih al-Bukhari 1: 211. See: Maraqi al-Falah, pp. 186-187.