Verse 12. Beat out - It is a metaphor from grain which was beaten out with a rod or staff, and then carefully gathered and laid up. From - From Euphrates to the Nile, which were the two borders of the land of promise. All the Israelites who are left in the land. One by one - Which signifies, God's exact care of them.
Verse 13. Trumpet - God shall summon them altogether by sound of trumpet, by an eminent call of his providence. He alludes to the custom of calling the Israelites together with trumpets.