John Gill

Strengthen ye the weak hands,.... These are the words of the prophet, as the Targum, "the prophet said, strengthen the weak hands;'' or rather of God, by the prophet, to the converted Gentiles, to those who saw the glory of the Lord; particularly to the ministers of the Gospel, who have to do with weak and feeble persons, who can scarcely lift up their hands, or stand upon their legs, under a sense of sin, in a view of wrath, and immediate ruin and destruction, ready to sink and faint, because of their enemies, or through want of food; and their business is to comfort and strengthen them, by preaching the Gospel, and pointing out the promises of it to them: and confirm the feeble knees; that so they may keep their ground against their enemies; shake off their fears and trembling; go on their way courageously and rejoicing; run, and not be weary; walk, and not faint: "hands" and "knees" are mentioned particularly, because a man's strength lies greatly in them; and his weakness is seen by the languor and trembling of them.