2 Corinthians 1:1-4
Paul, an Apostle of Jesus Christ through the will of God, and Timothy our brother, unto the Church of God, which is at Corinth, with all the saints which are in the whole of Achaia: grace to you and peace from God our Father and the Lord Jesus Christ. Blessed be the God and Father of our Lord Jesus Christ, the Father of mercies and God of all comfort; Who comfort us in all our affliction, that we may be able to comfort them that are in any affliction through the comfort wherewith we ourselves are comforted of God.
It is meet to enquire, first, why to the former Epistle he adds a second: and what can be his reason for thus beginning with the mercies and consolation of God.
Why then does he add a second Epistle? Whereas in the first he had said, “I will come to you, and will know not the word of them which are puffed up, but the power;” and again towards the end had promised the same in milder terms, thus, “I will come unto you when I shall have passed through Macedonia; for I do pass through Macedonia; and it may be that I shall abide, or even winter with you;” yet now after along interval, he came not; but was still lingering and delaying even though the time appointed had passed away; the Spirit detaining him in other matters of far greater necessity than these. For this reason he had need to write a second Epistle, which he had not needed had he but a little out-tarried his time.
Source: Homilies on Second Corinthians (New Advent)