This small midrash, "the heroic legend of the sons of Jacob", is based on Genesis 35:5 and 36:6, and recounts the story of the wars of Jacob and his sons against the kings of the Amorites and against Esau and his army.
That the legends contained in Vayisau are very old may be inferred from the Book of Jubilees[1] and from the Testament of Judah;[2] the midrash betrays its relationship to these old pseudepigraphical writings in many details.
The war against the Amorites is treated at greater length in the Sefer ha-Yashar, pericope "Beshallach."
The midrash itself is contained in Yalkut Shimoni,[3] and is mentioned by Naḥmanides as "Sefer Milchamot Benei Ya'akov".
[4] Strack & Stemberger (1991) cite the opinion of G. Schmitt that the work was composed not later than the Bar Kokhba war.