Abu Hurayrah reported: "I went out with the Messenger of Allah (ﷺ) and heard a man reciting Qul Huwa Allahu Ahad [Sūrah Al-Ikhlāṣ] so the Messenger of Allah (ﷺ) said: 'It is obligatory.' I said: 'What is obligatory?' He said: 'Paradise (is obligatory as a reward for the man).'" Reference: Jami` at-Tirmidhi 2897.