Adam Clarke on Exodus 23:18

The blood of my sacrifice with leavened bread - The sacrifice here mentioned is undoubtedly the Passover; (see Exo 34:25); this is called by way of eminence My sacrifice, because God had instituted it for that especial purpose, the redemption of Israel from the Egyptian bondage, and because it typified The Lamb Of God, who taketh away the sin of the world. We have already seen how strict the prohibition against leaven was during this festival, and what was signified by it. See on Exodus 12 (note).