So we see in this story [John 20:19-31], not only in the example with Thomas, but also in the example with the other disciples, what a very gracious Lord we have in Christ, who treats us neither sternly nor harshly, but seeks us out and comforts us as sheep gone astray. He does not say to the disciples, You have forsaken me, you were offended in me, you ran from me, and denied me, so now I do not want you any more; but he bears with long-suffering their weakness and does not make them suffer for the fact that they sinned so grossly against him and continue to sin. It is no small matter that they not only fell away from him before his sufferings, but now also after his resurrection are so unbelieving. This was written for our benefit and comfort, and to instruct us that, though unbelief is in complete opposition to him, nevertheless, he would regard it for our good, but only as long as we do not sin out of contempt for him but out of weakness. And so, that, in brief, is the message of this Gospel. The good Lord grant us his grace to comprehend it and keep it. Amen.
Martin Luther, sermon delivered on the first Sunday after Easter, 1534
Eugene F. A. Klug (Editor) Sermons of Martin Luther: The House Postils, volume 2 59