Joseph believes that, even if he wanted to, he cannot possibly take revenge. ‘Vengeance is mine’, says the Lord.
Doesn’t this mirror the way in which God deals with us. We repent of our sins through the work of the Holy Spirit, regenerating our hearts, working within, and we get the word of assurance from God: ‘Now therefore fear ye not: I will nourish you,’ and we are nourished; we are preserved right into the future, all the way home. We are comforted; we are given assurance. There is a nice translation here: ‘and speak kindly unto them’, and the original Hebrew actually says that he spoke to their hearts. He spoke to them in such a way that they would be moved and comforted. God does that to us too: moving us and comforting us. I hope your hearts don't grow cold and you cease to be moved by the word of God and the promises of God, and great answers to prayer, and God's dealings with you. Oh, the believer who ceases to be moved! Keep your heart warm always. In personal devotions, appreciate God's dealings with you. Turn them over in your mind: all his promises. What he has done for you from Calvary on, and let it warm your heart. It is so vital, because just as Joseph spoke to his brothers, speaking to their hearts, God speaks to our hearts. In your private devotions use your hymn book. Read the hymns and the verses. Relish them; think of them; let them move you. Be believers who are readily and constantly moved at the great goodness of God. That is how Joseph dealt with his brothers.
Who can do anything to thwart God’s purposes, when the things we try to do to stop his will coming to pass, are the very things he uses to bring about his will. We are so unskilful in our sin, and he is so skilful in his righteousness.