2Ti 1:15 This you know, that all those in Asia have turned away from me, …16 The Lord grant mercy to the household of Onesiphorus, for he often refreshed me, and was not ashamed of my chain; 17 but when he arrived in Rome, he sought me out very zealously and found me. 18 …—and you know very well how many ways he ministered to me at Ephesus.
Paul’s many friends in ministry disowned him in his time of need, primarily those in Asia as he notes here. Fast forward in 2Ti 4:16, “At my first defense no one came to stand by me, but all deserted me. May it not be charged against them! 17 But the Lord stood with me and strengthened me, … Also I was delivered out of the mouth of the lion”.
Despite of all these, one man, Onesiphorus, remained a true and faithful friend to Paul. Onesiphorus often visited him in prison and refreshed him with his presence and encouragements. He was not ashamed to be associated with a prisoner, often putting his life in harms way to visit and encourage Paul. He often traveled from far to find Paul never giving up. At Ephesus he had ministered to him perhaps financially or housed him whenever Paul was in town. This man had been very kind to him.
For his knowledge, Paul sought to inform Timothy that people will come into his life and most may leave in difficult times. But as in chapter 4, God will not leave him in his time of need. There will also be faithful friends like Onesiphorus who will be beneficial to him and Timothy should acknowledge and return the kindness. A good man will seek opportunities of doing good, and will not shun any that offer.