Issachar was the ninth son of Yaakov and the fifth son of Leah. The Torah explains his name through his mother's words: "God has given me my reward (sechari), for I gave my maidservant to my husband" (Genesis 30:18). He had four sons, Tola, Puvah, Yashuv and Shimron, who went down with him to Egypt; his tribe later received its inheritance in the Jezreel Valley.

In his blessing, Yaakov compares him to "a strong-boned donkey, crouching among the sheepfolds" who "bent his shoulder to the burden" (Genesis 49:14-15). Rashi explains that he bears the yoke of Torah like a strong donkey loaded with a heavy burden, and that his task was to decide matters of Torah law for all Israel and to fix the leap years.

The Book of Chronicles describes the sons of Issachar as men "who knew how to interpret the signs of the times, to determine how Israel should act", whose chiefs numbered two hundred (I Chronicles 12:33). Rashi understands these as two hundred heads of the Sanhedrin, who fixed the months and intercalated the years.

Moshe blessed the two brothers together: "Rejoice, Zebulun, in your going out, and Issachar, in your tents" (Deuteronomy 33:18). According to Rashi, Zebulun and Issachar formed a partnership: Zebulun, dwelling by the sea, traded and provided for Issachar, who devoted himself to Torah study, which is why Zebulun is mentioned first. This partnership remains the model for supporting Torah study.

According to Midrash Tadshe, Issachar was born on 10 Av and died at the age of one hundred and twenty-two. There are several traditions about his burial place: Sefer HaYashar places it in Sidon, together with Zebulun, and the Testaments of the Twelve Patriarchs in Hebron.