For the Gospel was not given that we might seek our own praise and glory through it or that the common people might acclaim us, its ministers, on account of it. But it was given that through it the blessing and glory of Christ might be illumined, that the Father might be glorified in His mercy, which He has shown us in Christ, His Son, whom He gave up for us and with whom He has given us all things (Rom. 8:32). Therefore the Gospel is the sort of teaching in which the last thing to look for is our own glory. It sets forth heavenly and eternal things which do not belong to us, which we have neither made nor earned, but which it offers to us in our unworthiness purely by the kindness of God. Then why should we lay claim to any glory on account of them? Therefore he who seeks his own glory in the Gospel speaks on his own authority. But he who speaks on his own authority is a liar, and there is unrighteousness in him; but He who seeks the glory of Him who sent Him tells the truth, and there is no unrighteousness in Him (John 7:18).
Luther’s Works, Volume 27, pages 100-101