Summary: Onesiphorus, a bold Christian who is otherwise unknown to us today, serves as a model of courage when he seeks out the imprisoned Apostle, Paul.
“May the Lord grant mercy to the household of Onesiphorus, for he often refreshed me and was not ashamed of my chains, but when he arrived in Rome he searched for me earnestly and found me—may the Lord grant him to find mercy from the Lord on that Day!—and you well know all the service he rendered at Ephesus.” 
One courageous act can ensure that the name of an individual will live on in honour. David became great, building his kingdom on the exploits of courageous individuals. The names of these bold men live on in honour. Among these bold men are some marked for honour by one courageous act. Shammah, for instance, was recognised for taking a stand in a field of lentils in battle against the Philistines [see 2 SAMUEL 23:11, 12]. Another of David’s mighty men appears to have distinguished himself repeatedly by bold, courageous acts. Benaiah the son of Jehoiada was recognised for vanquishing two ariels of Moab, for going into a pit with a lion on a snowy day and killing the beast, and for killing an Egyptian with the man’s own spear. Small wonder that David set this man over his bodyguard [see 2 SAMUEL 23:20-23]! Our text honours another man who is unknown to us other than for one courageous act.
Onesiphorus is mentioned only twice in the Bible. In our text, he is commended for his search for Paul despite the Apostle’s imprisonment. This was undoubtedly a courageous act. Paul will mention his family again in 2 TIMOTHY 4:19. Some scholars have concluded that Onesiphorus was dead, which would account for why Paul urges Timothy to greet his family though he fails to mention greeting Onesiphorus. Similarly, when the Apostle speaks of this good man in 2 TIMOTHY 1:16, he voices his prayer for mercy for Onesiphorus’ family without mentioning Onesiphorus. What is evident is that Onesiphorus was not with his family at the time Paul wrote. Onesiphorus was likely from Ephesus. We can infer that he and Paul became friends during the Apostle’s ministry there. In fact, whatever we may say concerning Onesiphorus is conjecture. His courage, however, is not a matter of conjecture.
A MODEL FOR CHRISTIAN COURAGE — “Onesiphorus … often refreshed me and was not ashamed of my chains, but when he arrived in Rome he searched for me earnestly and found me” [2 TIMOTHY 1:16, 17]. Onesiphorus is not addressed directly in this missive to Timothy. His family receives attention from the Apostle twice, however. In the text, the Apostle writes, “May the Lord grant mercy to the household of Onesiphorus” [2 TIMOTHY 1:16]. Then, Paul writes, “Greet … the household of Onesiphorus” [2 TIMOTHY 4:19]. It is strange that the Apostle greets “the household of Onesiphorus” and not Onesiphorus.
Several explanations can account for this apparent anomaly. Onesiphorus might have still been in Rome, ministering to the Apostle in prison. However, that possibility appears to be precluded by the fact that in our text, Paul uses the aorist tense when speaking of the ministry he had received from Onesiphorus. While the aorist tense is not strictly identical to our past tense in the English tongue, it does speak of an event without regard to how long the action was occurring or how long ago that action ceased. What is important is that the action is completed. Thus, we would surmise that Onesiphorus is no longer refreshing the Apostle.