{Purge out} (ekkatharate). First aorist (effective) active
imperative of ekkathair(935c), old verb to cleanse out (ek), to
clean completely. Aorist tense of urgency, do it now and do it
effectively before the whole church is contaminated. This turn to
the metaphor is from the command to purge out the old (palaian,
now old and decayed) leaven before the passover feast ( Ex
12:15f.  13:7  Zep 1:12 ). Cf. modern methods of disinfection
after a contagious disease. {A new lump} (
eon phurama). Make a
fresh start as a new community with the contamination removed.
Neos is the root for 
eaniskos, a young man, not yet old
(g(8872)aios). So new wine (oinon neon  Mt 9:17 ). Kainos is
fresh as compared with the ancient (palaios). See the
distinction in  Col 3:10  Eph 4:22ff.  2Co 5:17 . {Unleavened}
(azumoi). Without (a privative) leaven, the normal and ideal
state of Christians. Rare word among the ancients (once in
Plato). They are a new creation (kain(8820)ktisis), "exemplifying
Kant's maxim that you should treat a man as if he were what you
would wish him to be" (Robertson and Plummer). {For our passover
also hath been sacrificed, even Christ} (kai gar to pascha h(886d)(936e)
etuth(8820)Christos). First aorist passive indicative of 	hu(935c), old
verb to sacrifice. Euphony of consonants, 	h to 	 because of
-th(885c). Reference to the death of Christ on the Cross as the
Paschal Lamb (common use of pascha as  Mr 14:12  Lu 22:7 ), the
figure used long before by the Baptist of Jesus ( Joh 1:29 ).
Paul means that the Lamb was already slain on Calvary and yet you
have not gotten rid of the leaven.