2 Corinthians 1:3

After the foregoing preface, the apostle begins with the narrative of God's goodness to him and his fellow-labourers in their manifold tribulations, which he speaks of by way of thanksgiving to God, and to advance the divine glory (Co2 1:3-6); and it is fit that in all things, and in the first place, God be glorified. Observe, I. The object of the apostle's thanksgiving, to whom he offers up blessing and praise, namely, the blessed God, who only is to be praised, whom he describes by several glorious and amiable titles. 1. The God and Father of our Lord Jesus Christ: ho Theos kai patēr kuriou hēmōn Iēsou Christou. God is the Father of Christ's divine nature by eternal generation, of his human nature by miraculous conception in the womb of the virgin, and of Christ as God-man, and our Redeemer, by covenant-relation, and in and through him as Mediator our God and our Father, Joh 20:17. In the Old Testament we often meet with this title, The God of Abraham, and of Isaac, and of Jacob, to denote God's covenant-relation to them and their seed; and in the New Testament God is styled the God and Father of our Lord Jesus Christ, to denote his covenant-relation to the Mediator and his spiritual seed. Gal 3:16. 2. The Father of mercies. There is a multitude of tender mercies in God essentially, and all mercies are from God originally: mercy in his genuine offspring and his delight.

— Matthew Henry's Concise Commentary (public domain)

This thanksgiving for his late deliverance forms a suitable introduction for conciliating their favorable reception of his reasons for not having fulfilled his promise of visiting them (Co2 1:15-24). Father of mercies--that is, the SOURCE of all mercies (compare Jam 1:17; Rom 12:1). comfort--which flows from His "mercies" experienced. Like a true man of faith, he mentions "mercies" and "comfort," before he proceeds to speak of afflictions (Co2 1:4-6). The "tribulation" of believers is not inconsistent with God's mercy, and does not beget in them suspicion of it; nay, in the end they feel that He is "the God of ALL comfort," that is, who imparts the only true and perfect comfort in every instance (Psa 146:3, Psa 146:5, Psa 146:8; Jam 5:11).

— Jamieson-Fausset-Brown Commentary (public domain)