If the young man in the Gospel used this title in speaking to our Lord, it is only right that we should address Him in this way. He is indeed my Teacher in that He rules and teaches me. I am glad to run His errands and to sit at His feet. I am both His servant and His disciple and count it my highest honor to serve Him in this way. He is a good teacher. If He should ask me why I call Him "good," I could answer easily.
It is true that "no one is good except God alone,"1 but then He is God, and all the goodness of Deity shines in Him. In my experience I have found Him to be good, indeed so good that all the good I have has come to me through Him. He was good to me when I was dead in sin, for He raised me by His Spirit's power; He has been good to me in all my needs, trials, struggles, and sorrows. There could never be a better Teacher, for His service is freedom, His rule is love: I wish I were one thousandth part as good a servant. When He teaches me, He is unspeakably good, His doctrine is divine, His manner is gracious, His spirit is gentleness itself.
There is no error in His instruction: Pure is the golden truth that He presents, and all His teachings lead to goodness, sanctifying as well as edifying the disciple. Angels know that He is good and delight to worship at His footstool. The ancient saints proved Him to be a good Teacher, and each of them rejoiced to sing, "I am Your servant, O Lord!"
My own humble testimony must certainly be to the same effect. I will declare this before my friends and neighbors, for possibly they may be led by my testimony to seek my Lord Jesus as their Teacher. O I long that they might do so! They would never regret the decision. If they would submit to His easy yoke, they would find themselves in such royal service that they would never want to leave. The school of grace rejoices to have such a Teacher!
1) Mark 10:18.