Onesimus had been sent back to Colosse by Paul (more details about Onesimus are given in Paul’s letter to Philemon, the owner of the house in which the church in Colosse met, and who was the master from whom Onesimus had run away to Rome, where he had come in contact with Paul and had been converted). How does Paul describe Onesimus?
The apostle only speaks about information he can personally affirm. We see this detail in the pronoun ‘our’, which does not include the Colossians because he refers to them as ‘you’ (v. 10). That same use of pronouns also reveals that Paul’s opinion is shared by all who are with him. We cannot say how long Onesimus has been a Christian, but it cannot have been very long, probably a couple of years at most.
Onesimus has shown that he is now a trustworthy person. In this description we can see the power of the grace of God. Before his conversion, Onesimus had shown himself as a person not to be trusted, but having met Jesus he became a new man. So we see that followers of Jesus reveal very quickly that they are new creatures in Christ. Because this had happened, Paul could trust Onesimus with responsibilities in Colosse and elsewhere.
Further, Paul affirmed that Onesimus was as much a member of God’s family as himself – he was a beloved brother. The adjective is important because we know that sometimes brothers may not be loving. While one has to watch how much is read into a word, it is likely that ‘beloved’ points to ways that Onesimus revealed his love through service for Paul and his companions. Paul delighted in what he saw in Onesimus, which reminds us that we should take pleasure in observing the changed life that reveals spiritual growth.