Alleluia. Many of the preceding psalms and others which are to follow are prefaced by Alleluia, and the adornment of so many psalms with this heading seems hardly otiose. Just as in a melody this one general term embraces various tones, so the one word Alleluia incorporates manifold motives for expressing the force of its proclamation. There is more than one way of saying, "Bless the Lord," and just as this praise is assembled from different actions, so Alleluia is applied to various forms of activity and to appropriate discourses. The purpose of this psalm is to proclaim the perfection of the Law, in other words the Lord Christ, manifested to the world by mighty miracles from the beginnings of the Jewish nation; and the parallels between their situation and ours show that every Christian today is likewise set free.
The prophet speaks throughout the psalm. In the first section he recounts the miracles which the Lord bestowed on the Jews and on the Christian people. In the second he asks in the form of a question why the sea fled, and why the Jordan held back its course; to this he attaches the most pleasing reply that the earth was moved by the presence of the Lord. In the third section he shows that the idols of the Gentiles were unprofitable to their worshippers, and he then explains how useful and most wholesome is the Lord's religion to those who espouse it.
I. At the departure of Israel from Egypt, the house of Jacob from a barbarous people. We must here interpret departure as the time when we emerge from the chains of sins. We are freed from the mob of the Egyptians—in other words, of the demons—when we no longer endure the sovereignty of their barbaric harshness, when the ostentation