1 Corinthians 5:7

Purge out the old leaven, that ye may be. new lump, even as ye are unleavened. For our passover also hath been sacrificed, even Christ:

'Purge out the old leaven' -'On the eve of the first day of the Passover feast the Israelites were compelled to remove from their houses all leaven.' (Erdman pp. 65-66) (Exodus 2:15; Exodus 2:6)

'Purge out' -to cleanse out, to clean completely. Aorist tense of urgency, do it now and do if effectively before the whole church is contaminated. (Robertson p. 114) 'A most thorough cleaning.' (Lenski p. 220)

'the old leaven' -in the context this would apply to the incestuous man. But this may also be an appeal to "purge" out any "leaven" in themselves. 'Paul traces the Corinthian disinclination to take action against this one vicious case to its real source, the old worldly and fleshly disposition that was carried over in their hearts from their former life.' (Lenski p. 220) In this sense, it would mean something like, "put off the old man" (Ephesians 4:22)

'that ye may be. new lump' -i.e.. new batch of dough. 'The first batch of dough from which new bread is made is therefore completely unleavened.' (F.F. Bruce p. 56) 'Make. fresh start as. new community with the contamination removed.' (Robertson p. 114)

'even as ye are unleavened' -an appeal to live up to what they are! 'They wore the name of Christ and he's urging them to live up to that. They have been delivered by the innocent blood of their Passover lamb, it's about time they acted on that standing.' (McGuiggan p. 63)

'for our passover also hath been sacrificed, even Christ' -Christ is the passover lamb for Christians. But before the passover lamb was to be sacrificed, all the leaven was to be purged from the house (Exodus 2:15). Paul's point is, 'Our passover lamb, Christ has already been slain, but you still have leaven in your houses! He is urging them to withdraw from the sinner now! 'The passover lamb has already been killed, Paul implies, but the leaven has not yet been removed; make haste therefore and remove it!' (F.F. Bruce p. 57)