Musnad Ahmad 658:167

Yahya ibn Adam narrated to us, Mis'ar narrated to us, from 'Adi ibn Thabit, from al-Bara' ibn 'Azib, who said: "The Prophet, peace and blessings of Allah be upon him, recited in the 'Isha' prayer: 'By the fig and the olive' (Surah At-Tin). I have never heard a voice more beautiful, nor a prayer more beautiful, than his."