2 Timothy 1:3

I thank God
After the inscription and salutation follows the preface to the epistle; which contains a thanksgiving to God upon Timothy's account, and has a tendency to engage his attention to what he was about to write to him in the body of the epistle. God is the object of praise and thanksgiving, both as the God of nature and providence, and as the God of all grace; for every good thing comes from him, and therefore he ought to have the glory of it; nor should any glory, as though they had not received it: and he is here described, as follows,

whom I serve from my forefathers with pure conscience;
the apostle served God in the precepts of the law, as in the hands of Christ, and as written upon his heart by the Spirit of God, in which he delighted after the inward man, and which he served with his regenerated mind; and also in the preaching of the Gospel of Christ, in which he was very diligent and laborious, faithful and successful: and this God, whom he served, was the God of his "forefathers", of Abraham, Isaac, and Jacob, and of Benjamin, of whose tribe he was, and also of his more immediate ancestors. The Ethiopic version renders it, "from my original"; for though he preached the Gospel of Christ, and asserted the abrogation of the ceremonial law, yet he worshipped the one, true, and living God, the God of Israel, and was not an apostate from the true religion, as his enemies would insinuate: and this service of his was performed with a "pure conscience": every man has a conscience, but the conscience of every natural man is defiled with sin; and that is only a pure one, which is sprinkled and purged with the blood of Christ; and whereby a person is only fitted to serve the living God, without the incumbrance of dead works, and slavish fear, and with faith and cheerfulness; and such a conscience the apostle had, and with such an one he served God. For this refers not to his serving of God, and to his conscience, while a Pharisee and a persecutor; for however moral was his conduct and conversation then, and with what sincerity and uprightness soever he behaved, his conscience was not a pure one. He goes on to observe what he thanked God for,

that without ceasing I have remembrance of thee in my prayers night
and day;
that God had laid him upon his heart, and that he had such reason to remember him at the throne of grace continually. We learn from hence, that the apostle prayed constantly night and day; and if so great a man as he stood in need of continual prayer, much more we; and that in his prayers he was not unmindful of his friends, though at a distance from him; and in both these he is to be imitated: it becomes us to pray without ceasing: to pray always, and not faint and give out, to pray every day and night; and to pray for others as well as for ourselves, for all the saints, yea, for our enemies, as well as for our friends.