Albert Barnes on 2 Corinthians 4:1

Therefore, διατουτο. On account of this. That is, because the light of the gospel is so clear; because it reveals so glorious truths, and all obscurity is taken away, and we are permitted to behold as in a mirror the glory of the Lord, 2Cor 3:18. Since the glories of the gospel dispensation are so great, and its effects on the heart are so transforming and purifying, the object is to show the effect of being intrusted with such a ministry on the character of his preaching.

Seeing we have this ministry. The gospel ministry, so much more glorious than that of Moses, (2Cor 3:6;) which is the ministry by which the Holy Spirit acts on the hearts of men, 2Cor 3:8 which is the ministry of that system by which men are justified, (2Cor 3:9;) and which is the ministry of a system so pure and unclouded, 2Cor 3:9-11,18.

As we have received mercy. Tindal renders, this, "even as mercy is sure in us." The idea is, that it was by the mere mercy and favour of God that he had been intrusted with the ministry; and the object of Paul is doubtless to prevent the appearance of arrogance and self-confidence, by stating that it was to be traced entirely to God that he was put into the ministry. He doubtless had his eye on the fact that he had been a persecutor and blasphemer; and that it was by the mere favour of God that he had been converted and intrusted with the ministry, 1Timm 1:13. Nothing will more effectually humble a minister, and prevent his assuming any arrogant and self-confident airs, than to look over his past life; especially if his life was one of blasphemy, vice, or infidelity; and to remember that it is by the mere mercy of God that he is intrusted with the high office of an ambassador of Jesus Christ. Paul never forgot to trace his hope, his appointment to the ministerial office, and his success, to the mere grace of God.

We faint not. This is one of the effects of being intrusted with such a ministry. The word here used (εκκακουμεν) means, properly, to turn out a coward; to lose one's courage; then to be faint-hearted, to faint, to despond, in view of trial, difficulty, etc.--Robinson. Here it means, that by the mercy of God he was not disheartened by the difficulties which he met; his faith and zeal did not flag; he was enabled to be faithful, and laborious, and his courage always kept up, and his mind was filled with cheerfulness. 2Cor 2:14. He was deterred by no difficulties; embarrassed by no opposition; driven from his purpose by no persecution; and his strength did not fail under any trims. The consciousness of being intrusted with such a ministry animated him; and the mercy and grace of God sustained him.

(a) "received mercy" 1Cor 7:25