Keil & Delitzsch

Jehovah has wrought out salvation through judgment in the sight of all the world. "Jehovah hath made bare His holy arm before the eyes of all nations, and all the ends of the earth see the salvation of our God." As a warrior is accustomed to make bare his right arm up to the shoulder, that he may fight without encumbrance (exsertare humeros nudamque lacessere pugnan, as Statius says in Theb. i. 413), so has Jehovah made bare His holy arm, that arm in which holiness dwells, which shines with holiness, and which acts in holiness, that arm which has been hitherto concealed and therefore has appeared to be powerless, and that in the sight of the whole world of nations; so that all the ends of the earth come to see the reality of the work, which this arm has already accomplished by showing itself in its unveiled glory - in other words, "the salvation of our God."