Deuteronomy 16:3

16:3 You must not eat any yeast with it; for seven days you must eat bread made without yeast, symbolic of affliction, for you came out of Egypt hurriedly. You must do this so you will remember for the rest of your life the day you came out of the land of Egypt.

Deuteronomy 25:5

Respect for the Sanctity of Others

25:5 If brothers live together and one of them dies without having a son, the dead man’s wife must not remarry someone outside the family. Instead, her late husband’s brother must go to her, marry her, and perform the duty of a brother-in-law.