Often in prophecy events that will happen in the future are described as something that has already happened. This emphasizes that the event will certainly happen. Here "Issachar" refers to his descendants. They are compared to a donkey. This emphasizes that they will work very hard. Alternate translation: "The descendants of Issachar will be like a strong donkey." (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])