Thomas, looking into the face of his Lord, said to Him, "My Lord and my God." "My Lord" is a confession of the absolute sovereignty of Jesus, and therefore a confession of absolute submission to Him. Yet, had there been no other word spoken, it would not have arrested our attention, or perhaps demanded so serious consideration. The disciples had called Him Lord so often. The title Lord as used at the time had, in some cases, no more significance than the title "Sir" as we use it in addressing men today. As it fell from the lips of this man, however, I think I am warranted in saying it came with full and rich meaning. Thomas, saying to Christ upon that occasion "My Lord," did in that word recognize the sovereignty of Christ over his own life, and did by that word yield himself in willing submission to that sovereignty.
The second word of the great confession is even more arresting, and, indeed, it is by the second that I interpret the value of the first. Not only "My Lord," not only the One Who is sovereign over my life and to Whom I am prepared to render whole-hearted submission, but "My God." The word stands without exception for absolute Deity; and therefore indicated, on the part of the man who employed it, that he bowed before the One so addressed not only in submission but in worship. "My Lord," the confession of sovereignty and of submission; "My God," the confession of Deity and of worship.
Adapted from Was Thomas Mistaken?, by G. Campbell Morgan.