Charles Ellicott Commentary 2 Corinthians 4:13

"But having the same spirit of faith, according to that which is written, I believed, and therefore did I speak; we also believe, and therefore also we speak;" — 2 Corinthians 4:13 (ASV)

We have the same spirit of faith...—The “spirit of faith” is not definitely the Holy Spirit, but the human spirit in fellowship with the Divine, and therefore characterized by faith. And then, as if pleading that this faith must find utterance, he falls back on the words that are in his mind, almost as an axiom, from Psalms 116:10: I believed, and therefore I spoke.

It will be noted that the context of the words quoted is eminently in harmony with the feelings to which the Apostle has just given expression: The sorrows of death encompassed me; the pains of hell got hold of me. I found trouble and heaviness... I was brought low... You have delivered my soul from death (Psalms 116:3–8). It is as though that Psalm had been his stay and comfort in the midst of his daily conflict with disease.