The Lord give mercy unto the house of Onesiphorus; for he oft refreshed me, and was not ashamed of my chain:
The Lord give mercy - as Onesiphorus had showed mercy.
The house of Onesiphorus. He was then absent from Ephesus which accounts for the expression (2 Timothy 4:19). He had not yet returned from his visit at Rome (2 Timothy 1:17). His household would hardly retain his name after the master was dead. Nowhere bus Paul prayers for the dead, which is fatal to the theory that he was dead. God blesses not only the righteous man himself, but all his household: even as a good man's household generally join in his good deeds.
My chain. Paul, in the second, as in his first imprisonment, was bound by a chain to the soldier who guarded him ('custodia militaris').