He was a fisherman's son and held the false view that, according to the Buddha's teaching, a man's consciousness runs on and continues without break of identity.
Sāti's colleagues did their best to change his way of thinking, but failing to do so, they reported the matter to the Buddha. He questioned Sāti, who, however, sat silent and glum; then the Buddha preached to him and the assembled monks the Mahātanhāsankhaya Sutta (M.i.256 ff).
Buddhaghosa explains (MA.i.477) that Sāti was not a learned man. He knew only the Jātakas, and his views were due to the fact that in the Jātakas various characters were identified with the Buddha.