Therefore let us keep the feast — Let us feed on him by faith. Here is a plain allusion to the Lord's supper, which was instituted in the room of the passover. Not with the old leaven — Of heathenism or Judaism. Malignity is stubbornness in evil. Sincerity and truth seem to be put here for the whole of true, inward religion.
Related Commentaries of 1 Corinthians 5:8
1 Corinthians 5:8
8 Therefore let us keep the feast,c not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.