Exodus 13:7

13:7 Bread made without yeast must be eaten for seven days; no bread made with yeast shall be seen among you, and you must have no yeast among you within any of your borders.

Exodus 23:21

23:21 Take heed because of him, and obey his voice; do not rebel against him, for he will not pardon your transgressions, for my name is in him.