פירוש על עבודה זרה 49:2

The rabbis now try to find a verse in Genesis that hints at the episode of the sun standing still. In Jacob’s blessing at the end of the work, he foresees that Ephraim’s seed will “fill the nations.” The simple reading is probably that the tribe of Ephraim will be numerous. But the midrashic meaning is taken to be that Ephraim’s fame will fill the nations when a member of the tribe performs a wondrous act.

According to R. Joshua b. Levi the sun stood still for an extra 12 hours, such that the day which should take a total of 12 hours, actually took a total of 24 hours.