1 Corinthians 5:7-8; 1 Peter 1:19

7 Therefore purge out the old leaven, that you may be a new lump, since you truly are unleavened. For indeed Christ, our Passover, was sacrificed for us. 8 Therefore let us keep the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.
19 but with the precious blood of Christ, as of a lamb without blemish and without spot.