Psalms 40:3

3. And he hath put into my mouth a new song In the first clause of the verse he concludes the description of what God had done for him. By God’s putting a new song into his mouth he denotes the consummation of his deliverance. In whatever way God is pleased to succor us, he asks nothing else from us in return but that we should be thankful for and remember it. As often, therefore, as he bestows benefits upon us, so often does he open our mouths to praise his name. Since God, by acting liberally towards us, encourages us to sing his praises, David with good reason reckons, that having been so wonderfully delivered, the matter of a new song had been furnished to him. He uses the word new in the sense of exquisite and not ordinary, even as the manner of his deliverance was singular and worthy of everlasting remembrance. It is true, that there is no benefit of God so small that it ought not to call forth our highest praises; but the more mightily he stretches forth his hand to help us, the more does it become us to stir up ourselves to fervent zeal in this holy exercise, so that our songs may correspond to the greatness of the favor which has been conferred upon us.

Many shall see it Here the Psalmist extends still farther the fruit of the aid which he had experienced, telling us, that it will prove the means of instruction common to all. And certainly it is the will of God that the benefits which he bestows upon any individual of the faithful should be proofs of the goodness which he constantly exercises towards all of them, so that the one, instructed by the example of the other, should not doubt that the same grace will be manifested towards himself. The terms fear, and hope, or trust, do not seem at first view to harmonise; but David has not improperly joined them together; for no man will ever entertain the hope of the favor of God but he whose mind is first imbued with the fear of God. I understand fear in general to mean the feeling of piety which is produced in us by the knowledge of the power, equity, and mercy of God. The judgment which God executed against the enemies of David served, it is true, to inspire all men with fear; but, in my opinion, David rather means, that by the deliverance which he had obtained, many would be induced to yield themselves to the service of God, and to submit with all reverence to his authority, because they would know him to be the Judge of the world. Now, whoever submits cordially to the will of God will of necessity join hope with fear; especially when there is presented to his view the evidence of the grace by which God commonly allures all men to himself; for I have already said that God is presented to our view as merciful and kind to others, that we may assure ourselves that he will be the same towards us. As to the word see, of which David makes use, we are to understand it as referring not only to the eyes, but chiefly to the perception of the mind. All without distinction saw what had happened, but to many of them it never occurred to recognize the deliverance of David as the work of God. Since, then, so many are blind regarding the works of God, let us learn, that those only are considered to see clearly to whom the Spirit of understanding has been given, that they may not occupy their minds in dwelling upon the mere events which take place, but may discern in them by faith the secret hand of God.