That good thing which was committed unto thee; - see the notes at 1 Timothy 6:20. The reference here in the phrase, “that good thing committed to thee,” is to the sound Christian doctrine with which he had been intrusted, and which he was required to transmit to others.
Keep by the Holy Ghost - By the aid of the Holy Spirit. One of the best methods of preserving the knowledge and the love of truth is to cherish the influences of the Holy Spirit.