Albert Barnes Commentary Psalms 27:13

"[I had fainted], unless I had believed to see the goodness of Jehovah In the land of the living." — Psalms 27:13 (ASV)

I had fainted, unless I had believed - The words “I had fainted” are supplied by the translators, but they undoubtedly express the true sense of the passage. The psalmist refers to the state of mind produced by the efforts of his enemies to destroy him, as mentioned in (Psalms 27:12).

So numerous, mighty, and formidable were they, that he says his only support was his faith in God; his belief that he would yet be permitted to see the goodness of God upon the earth. In this time of perplexity and trial, he had confidence in God and believed that He would uphold him and permit him to see the evidences of His goodness and mercy while yet on the earth. What was the ground of this confidence he does not say, but he had the fullest belief that this would be so.

He may have had some special assurance of it, or he may have had a deep internal conviction of it, sufficient to calm his mind; but whatever was the source of this confidence, it was that which sustained him. A similar state of feeling is indicated in the remarkable passage in Job (Job 19:25–27). See the notes at that passage.

To see the goodness of the Lord in the land of the living - That is, that I should “live,” and yet see and enjoy the tokens of the divine favor here upon the earth.