2 Since we are thus circumstanced, my brethren, let us never loiter in the path of virtue; for hereto he counsels us, saying, 'Be followers of me, as I also am of Christ.' For he gave this advice not to the Corinthians only, since he was not their Apostle only, but being 'a teacher of the Gentiles in faith and verity,' he admonished us all through them; and in short, the things he wrote to each particular person are commandments common to all men. On this account in writing to different people, some he exhorted as, for instance, in the Epistles to the Romans, and the Ephesians, and Philemon.
Some he reproved, and was indignant with them, as in the case of the Corinthians and Galatians. To some he gave advice, as to the Colossians and Thessalonians. The Philippians he approved of, and rejoiced in them. The Hebrews he taught that the law was a shadow to them. But to his elect sons, Timothy and Titus, when they were near, he gave instruction; when far away, he put them in remembrance. For he was all things to all men; and being himself a perfect man, he adapted his teaching to the need of every one, so that by all means he might rescue some of them. Therefore his word was not without fruit; but in every place it is planted and productive even to this day.
Source: Letters (New Advent)