Charles Ellicott 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)

And again, Isaiah says.—St. Paul still adheres to the Septuagint, which here diverges more widely from the Hebrew text. The meaning of this is correctly given by the Authorized Version of Isaiah 11:10—“In that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek.” (Isaiah 11:10). In either case the passage is Messianic.

A root of Jesse.—Strictly, the root, or, root-shoot of Jesse, as in Proverbs 5:5—i.e., the expected descendant of Jesse’s line, which, to bring out its intimate connection with the founder of the line, and to distinguish it from all other collateral branches, is identified with the very root, or first shoot, of the line itself.

Trust.—The same word as “hope” in the next verse, the introduction of which was probably suggested, through the association of ideas, by the concluding words of the Septuagint quotation—“On Him shall the Gentiles place their hopes. Now the God of hope, etc.”