Moreover, thou son of man, take thee one stick, and write upon it, For Judah, and for the children of Israel his companions: then take another stick, and write upon it, For Joseph, the stick of Ephraim, and for all the house of Israel his companions: 17And join them one to another into one stick; and they shall become one in thine hand.
Ezekiel 37:16-17
The nation of Israel was divided in the course of God judging them. The 10 northern tribes went into captivity first and spread throughout the world. These tribes are called Joseph and Ephraim. The southern tribes of Judah and Benjamin were taken later into Babylon.
In the millennium, the one-thousand-year reign of Christ on earth, the nation of Israel will be joined back together and be restored.
Ezekiel 37:19 Say unto them, Thus saith the Lord GOD; Behold, I will take the stick of Joseph, which is in the hand of Ephraim, and the tribes of Israel his fellows, and will put them with him, even with the stick of Judah, and make them one stick, and they shall be one in mine hand.
Ezekiel 37:22 And I will make them one nation in the land upon the mountains of Israel; and one king shall be king to them all: and they shall be no more two nations, neither shall they be divided into two kingdoms any more at all: