1. Moses gives the People a second chance
Exodus 34:1-9,27-35.

2. The Thirteen Virtues
Exodus 34:6(part)-7(part).

3. Variations on the Thirteen Virtues
Numbers 14:18
Joel 2:13
Nahum 1:3
Psalms 86:15; 103:8; 111:4; 116:5; 145:8
2 Chronicles 30:9
Nehemiah 9:17,31

4. Animal tithes
Leviticus 27:32-33

5. ELLUL occurs as an acronym
Deuteronomy 30:6 (Et Levavekha …)
Song of Songs 6:3 (Ani Ledodi …)
Esther 9:22 (Ish Lere'ehu …)

6. Shulhan Aruch, Orah Hayyim (and Mishnah Berurah) §§ 581.

7. Kitzur Shulhan Aruch §§ 128:5,6,7,9,10.

8. Sefer Hatoda'ah (by E.Ki-Tov) : Chapter on 'Ellul'.

9. Pirkei de Rabbi Eliezer: The custom of blowing the Shofar during Ellul.

10. The Selihot Prayers.