According to Moses, God told the people not to eat bread that has yeast in it, and instead, they should eat bread without yeast in all the places they live. This was a special rule to remember an important event where God helped them.
Exodus 12:20: Ye shall eat nothing leavened; in all your habitations shall ye eat unleavened bread.
These verses imply that Jesus declared all foods clean, contradicting the restriction in Exodus 12:20 on leavened bread during Passover.
Mark 7:18-19: Because it entereth not into his heart, but into the belly, and goeth out into the draught, purging all meats?