John Calvin Commentary Deuteronomy 30:4

"If [any of] thine outcasts be in the uttermost parts of heaven, from thence will Jehovah thy God gather thee, and from thence will he fetch thee:" — Deuteronomy 30:4 (ASV)

If any of thine be driven out. Since their dispersion into unknown countries might have entirely annihilated their hope of restoration, Moses anticipates this doubt. He teaches them that even though they might be driven out into the farthest regions of the earth, the infinite power of God was sufficient to gather them from there, as it is also said in Psalm 147:2:

The Lord doth build up Jerusalem; he gathereth together the outcasts of Israel.

With this intent, the adverb “from there” is repeated twice, so that they would not imagine that distance of place would be any obstacle to the fulfillment of what God had promised.

We have seen elsewhere that it was for good reason their dwelling in the land of Canaan was emphasized as a special blessing.

This was because, until the time of Christ’s coming, it was necessary for the hope of an eternal inheritance to be cherished in their minds through an earthly and visible symbol.