Exposition of the Old and New Testament, by John Gill, [1746-63], at sacred-texts.com
That this epistle was written to Timothy, while he was at Ephesus, where the apostle in his former epistle had desired him to stay, is evident from his making mention of some persons in it, who were Ephesians; as Onesiphorus, whom he commends, and Alexander the coppersmith, of whom he complains: and that this epistle was written by the apostle, when he was at Rome, is no less evident; for he expressly calls himself a prisoner, Ti2 1:8 and speaks of being then in trouble, and in bonds, Ti2 2:9 and the persons that send their salutations in it to Timothy were Romans, Ti2 4:21 but at what time it was written is not so certain: it seems by Ti2 4:7 that it was but a little time before his martyrdom; though those words may only signify, that he was now very much on the decline of life, was now grown an old man, and in continual expectation of death, and was in a constant readiness for it, come when it would; having faithfully discharged his duty, and his warfare being as good as accomplished, and his race almost run out; for he afterwards presses Timothy to come to him, and that before winter; and desires him to bring with him his cloak, books, and parchments, which one would think he would have little occasion for, if just upon his martyrdom: besides, he says he was delivered out of the mouth of the lion, that by him the preaching of the Gospel might be fully known, and that all the Gentiles might hear it; and expresses his confidence, that he should be again delivered, Ti2 4:9. And it looks as if this epistle was written before the epistles to the Philippians, Colossians, and Philemon, since it appears that Timothy did come to him at Rome; as here desired, and is joined with the apostle in those epistles. Some, therefore, have placed this epistle in the year 58, or 59, about the fourth or fifth of Nero's reign. The design of it is to stir up Timothy to the faithful and diligent discharge of his duty, as a minister of the Gospel; to abide constantly by the truths of it, and to animate him to suffer patiently, cheerfully, and courageously for the sake of it; and to warn him against false teachers, and their errors, who were already risen, and would afterwards arise, and be followed by such who had itching ears, and could not bear sound doctrine; but this should be no discouragement to him in the prosecution of his work; and lastly to desire his presence with him at Rome, being now destitute of his several assistants.