Not the sinful man, but evil of every kind, in accordance with the more general statement of the leavening, power of evil in 1Co 5:6. The apostle's metaphor is shaped by the commands concerning the removal of leaven at the passover: Exo 12:19; Exo 13:7. Compare Ignatius; “Dispense, therefore, with the evil leaven that has grown old (παλαιωθεῖσαν) and that has gone sour (ἐνοξίσασαν), and be changed into new leaven which is Jesus Christ” (Epistle to Magnesians, 10).