Adam Clarke on 1 Corinthians 5:7

Purge out therefore the old leaven - As it is the custom of the Jews previously to the passover to search their houses in the most diligent manner for the old leaven, and throw it out, sweeping every part clean; so act with this incestuous person. I have already shown with what care the Jews purged their houses from all leaven previously to the passover; see the note on Exo 12:8-19 (note), and on the term passover, and Christ as represented by this ancient Jewish sacrifice; see on Exo 12:27 (note), and my Discourse on the Nature and Design of the Eucharist.