Matthew Poole and continuators on Genesis 49:14

14 Issachar is a strong ass , couching down between two burdens .

Heb. an ass of bone, (i. e.) of great bulk and bones, and strength of body, but of little spirit and courage.

Which are laid upon his back, and which he is contented to bear. Or, lying down, i. e. enjoying his ease and rest, between the borders, to wit, of the other Tribes, with which he was encompassed and secured from forreign enemies, which made him more secure and slothful. Or, between the orders or folds of cattle, as a word very near akin to it, and proceeding from the same root signifies, Iudg. 5. 16. to the feeding and minding whereof he wholly gave himself, neglecting more generous things.