‘Amr b. Shu'aib, on his father’s authority, quoted his grandfather as saying that the Prophet said, “The best supplication is that on the day of ‘Arafa, and the best thing which I and the prophets before me have said is, ‘There is no god but God alone who has no partner; to Him belongs the dominion, to Him praise is due, and He is omnipotent’.’’
Tirmidhi transmitted it, and Malik transmitted on the authority of Talha b. ‘Ubaidallah up to “who has no partner.”