Narrated Ali ibn AbuTalib:

A man of the Ansar called him and AbdurRahman ibn Awf and supplied them wine before it was prohibited. Ali then led them in the evening prayer, and he recited; "Say: O ye who reject faith." He was confused in it. Then the following verse came down: "O ye who believe! approach not prayers with a mind befogged until you can understand all that ye say.