Numbers 20:29

20:29 When all the community saw that Aaron was dead, the whole house of Israel mourned for Aaron thirty days.

Deuteronomy 21:13

21:13 discard the clothing she was wearing when captured, and stay in your house, lamenting for her father and mother for a full month. After that you may have sexual relations with her and become her husband and she your wife.

Deuteronomy 34:8

34:8 The Israelites mourned for Moses in the deserts of Moab for thirty days; then the days of mourning for Moses ended.