Though Reuben deserve to be cut off, or greatly diminished and obscured, according to Jacob's prediction, Genesis 49:4; yet God will spare them, and give them a name and portion among the tribes of Israel, and bless them with increase of their numbers.
Related Commentaries of Deuteronomy 33:6
Deuteronomy 33:6
6 Let Reuben live, and not die; and let not his men be few.