Albert Barnes Commentary Psalms 40:3

"And he hath put a new song in my mouth, even praise unto our God: Many shall see it, and fear, And shall trust in Jehovah." — Psalms 40:3 (ASV)

And he has put a new song in my mouth — See the notes at Psalm 33:3. The idea is that he had given a new or fresh “occasion” for praise. The deliverance was so marked, and was such an addition to former mercies, that a new expression of thanks was proper.

It was an act of such surprising intervention on the part of God that the language used on former occasions, and which was adapted to express the mercies then received, would not be sufficient to convey the sense of gratitude felt for the present deliverance.

As applied to the Messiah, and referring (as it was supposed in the notes at Psalm 40:2) to his being raised up to glory after the depth of his sorrows, it would mean that no language previously employed to express gratitude to God would be adequate to the occasion, but that the language of a new song of praise would be demanded to celebrate so great an event.

Even praise to our God — “To our God;” identifying himself, as the Messiah does, with his people, and expressing the idea that the new song of praise was appropriate to them as well as to “himself,” since they would be benefited by his work, and since God was their God as well as his. Compare John 20:17.

Many shall see it — Great numbers of the human race shall be made acquainted with the occasion which there was for such a song.

And fear — Learn to reverence, to worship, to honor God, as the result of what had been done.

And shall trust in the Lord — Shall confide in God; shall put their trust in him; shall become his true worshippers and friends:

• as the effect of this merciful interposition in behalf of him who had been so in trouble or distress, and who was enabled to triumph;
• as the result of the work accomplished by him.

The effect of the Redeemer’s sorrows, and of God’s merciful help, would be that great numbers would learn to put their trust in God, or would become his true friends. No man, in fact, can compute the numbers of those who, in consequence of the work of the Messiah, will turn to God and become his true worshippers and friends.