Albert Barnes Commentary Romans 15:12

"And again, Isaiah saith, There shall be the root of Jesse, And he that ariseth to rule over the Gentiles; On him shall the Gentiles hope." — Romans 15:12 (ASV)

Isaiah says (Isaiah 11:1, 10):

There shall be a root. A descendant, or one who would proceed from him when he was dead. When a tree dies and falls, a root may remain that will retain life and send up a sprout of a similar kind.

So Job says (Job 14:7), For there is hope of a tree, if it be cut down, that it will sprout again, and that the tender branch thereof will not cease. So, in relation to Jesse, though he should fall like an aged tree, yet his name and family would not be extinct.

There would be a descendant who would rise and reign over the Gentiles. The Lord Jesus is also called the root and the offspring of David (Revelation 22:16; Revelation 5:5).

Of Jesse. The father of David (1 Samuel 17:58). The Messiah was thus descended from Jesse.

He that shall rise. That is, as a sprout springs up from a decayed or fallen tree. Jesus thus rose from the family of David, which had fallen into poverty and humble life in the time of Mary.

To reign over the Gentiles. This is quoted from the Septuagint of Isaiah 11:10. The Hebrew is, Which shall stand up for an ensign of the people; that is, a standard to which they will flock. Either the Septuagint or the Hebrew would express the idea of the apostle. The substantial sense is retained, though it is not literally quoted. The idea of his reigning over the Gentiles is one that is fully expressed in the second psalm.

In him, etc. The Hebrew is, To it shall the Gentiles seek. The sense, however, is the same. The design of this quotation is the same as the preceding: to show that it was predicted in the Old Testament that the Gentiles would be made partakers of the privileges of the gospel. The argument of the apostle is that if this was designed, then converts to Christianity from among the Jews should lay aside their prejudices and receive them as their brethren, entitled to the same privileges of the gospel as themselves. The fact that the Gentiles would be admitted to these privileges, the apostle had more fully discussed in chapters 10 and 11.