Jamieson, Fausset and Brown on Colossians 4:9

9. Onesimus--the slave mentioned in the Epistle to Philemon (Phm 10, 16), "a brother beloved."

a faithful ... brother--rather, "the faithful brother," he being known to the Colossians as the slave of Philemon, their fellow townsman and fellow Christian.

one of you--belonging to your city.

They shall make known unto you all things--Greek, "all the things here." This substantial repetition of "all my state shall Tychicus declare unto you," strongly favors the reading of English Version in Col 4:8, "that he might (may) know your state," as it is unlikely the same thing should be stated thrice.