Hassidout sur La Genèse 49:14

Issachar is a strong-boned ass, crouching down between the stables (Gen. 49:14). In the name of Rabbi Israel Ba’al Shem, on the verse Issachar is a strong-boned [garem] donkey: that is to say, there is reward [s’khar] by way of that which the “donkey” causes [gorem]. (Tzava'at HaRivash p.12b)

In the name of the Ba’al Shem Tov, this is the explanation: “There is reward that the ‘donkey’ [hamor] causes,” meaning by way of food and drink, which are physical [homer] matters, he causes this reward – by way of his elevating to the Cause of Elevation the holy spark that was crouching down between the stables, which was among the lower elements. (Or HaGanuz le-Tzadikim, Vayehi)

Genesis 49,14-15. “Issachar is a strong-boned ‎donkey;” Yaakov sees in the name ‎יששכר‎ which contains the ‎word ‎שכר‎, “reward,” an allusion to the relationship between the ‎body’s exertion in fulfilling the commandments on the one hand, ‎and the spiritual reward resulting from this, on the other. The ‎body pulls in one direction, earthward, whereas the reward ‎compensates by pulling in the opposite direction, i.e. heaven-‎oriented.‎