Charles Ellicott Commentary Psalms 110:2

"Jehovah will send forth the rod of thy strength out of Zion: Rule thou in the midst of thine enemies." — Psalms 110:2 (ASV)

Send.—The verb should be rendered here as stretch, as in Genesis 22:10 and Genesis 48:14, and it frequently refers to stretching out the hand, often with hostile intent. The poet here speaks in his own person, addressing the King to whom the oracle has just been announced.

Rod of thy strength—that is, the scepter, which is the emblem of royal power and sway . The word staff is different from that rendered rod in Psalm 2:9; and the image is not, as there, necessarily of a weapon of destruction, but only of kingly rule, as in Psalm 45:6.

Rule thou ...—It is better to take these words as a quotation and understand them as spoken of Jehovah. In the picture before us, the Divine King seats the earthly monarch by His side and, taking his scepter from his hand, stretches it as a token of the wide empire he is to administer from Zion (where they sit enthroned) over the surrounding nations, and bids him assume the offered sway, in spite of the enemies that surround him at present.

The expression in the midst, instead of over, implies the condition under which the sovereignty was to be assumed, as does the rest of the psalm, which proceeds to describe the wars by which ultimate triumph over the hostile tribes would be secured.