Deuteronomy 30:1
And it shall come to pass, when all these things are come upon thee, the blessing and the curse, which I have set before thee, and thou shalt call them to mind among all the nations, whither the LORD thy God hath driven thee, And it shall come to pass, when all these things are come upon thee, the blessing and the curse, which I have set before thee, and thou shalt call them to mind among all the nations, whither the LORD thy God hath driven thee,
Moses looks beyond settlement in Canaan, when each tribe would be in its own possession, to foretell Israel's long future of apostasy and its punishment. Both the blessing and the curse set before Israel would actually come upon them. Because of their sins God Himself would drive and scatter them as captives among the nations, into heathen and strange lands, with the glory departed from Israel, their beautiful city in ruins and the people captives in strange lands.
Among those nations where the Lord had driven them they would call the blessing and the curse to mind and recall them. The message was so important it was to be put into a song to be sung by all Israel so it would not be forgotten. That remembering would lead to returning to God in penitence and obedience, obeying His voice with all the heart and soul together with their children, keeping His commandments in loyalty, truth and submission.
To such repentance after judgment God promises compassion, pardon, gathering, and re-establishment in their own land with restored strength. The scattering into heathen lands was meant to carry the knowledge of God's truth to the world. The prediction was fulfilled to the letter when God permitted His chosen people to be scattered as captives in strange lands and, upon their repentance, took them back and established them again in their own land.
The fulfillment of the scattering warning gave Nehemiah assurance that God would also keep His promise to restore His people and their strength. After that restoration, continual disobedience brought complete overthrow including the overthrow of Jerusalem. The foretold sequence runs through dispersion and restoration to the land of the fathers before coming at last under Roman dominion.