My Lord, to whom I wholly yield and give up my self; and my God, in whom I believe. It is observed, that this is the first time that in the Gospel the name of God is given to Christ; he was now by his resurrection declared to be the Son of God with power, Revelation 1:4. So as Thomas did not show more weakness and unbelief at the first, than he showed faith at last, being the first that acknowledged Christ as God over all blessed for ever, the object of people's faith and confidence, and his Lord, to whom he freely yielded up himself as a servant, to be guided and conducted by him.
Related Commentaries of John 20:28
John 20:28
28 And Thomas answered and said unto him, My Lord and my God.