From a sermon Martin Luther preached in 1534:
In this manifestation [of Jesus to the disciples in John 20:19-31], there are other teachings and examples which are useful and comforting. First, it is good to note that the Lord does not wait for his disciples to go after him, but he goes after them, through locked doors, greets them in a friendly manner, comforts and strengthens them in the faith of his resurrection. He could not have done it in a kindlier manner than to offer them peace and show them his hands and side, so that they would be sure of his resurrection and would be comforted against all sorrow, fear, and terror. There is nothing unpleasant or fearful here. The greeting is sweet and pleasing. For “peace” in Hebrew signifies all good, happiness, and well-being. “…
With this example Christ presents his heart, who he is, and what kind of heart and will he bears to us, as a comfort to all troubled, frightened, and fearful hearts, that they may hope for all good things and every kindness from him. He comforts and strengthens his disciples who love him and rejoice at his coming, as the Evangelist says, “The disciples were glad when they saw the Lord.” But the others, who despise him, as the Jews do [obviously, Luther does not mean the Jews who became disciples of Jesus or those who have not heard the Gospel, but those who have heard it, rejected it, and despise it, like Caiaphas. In this, Luther uses the word “Jews” like John does in his Gospel.] he will punish at the proper time. We should come to know Christ in this way: He is kindly disposed and comforting to all the poor who are needy and anxious; on the other hand, he is a severe judge of all who despise him. To know him this way is to know him rightly.
Therefore we should expect from Christ all love, kindness, comfort, salvation, and encouragement, and call on him in perils of fire, perils of water, in death, and in all assaults on your faith. For he is also the only cornerstone, to whom we should hold in all our troubles. If you fall into the fire, or water, if you are dying, hold firmly to him, and say, Lord, I know you will not forsake me, you will help me through.
This is the first part of this lesson: Christ treats his disciples so tenderly, does not reproach them for their unbelief, sin, or weakness, but comforts, strengthens, and lifts them up. This was done for our good and comfort. The devil assaults us without letup, as St. Peter says (1 Peter 5:8): “Your adversary the devil, as a roaring lion walketh about, seeking whom he may devour,” and, therefore, we need to keep this example of Christ’s kindness and love to us well in mind, so that we know how to take comfort and stand fast against the enemy.
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 55-56