Then He charged them, saying, "Take heed, beware of the leaven of the Pharisees and the leaven of Herod." (Mark 8:15)
In the Name + of Jesus. Amen. Leaven makes things grow. In the case of the Pharisees and Herod, it's their egos. "Hey, look at me, God! Look at me and how much I keep the Law!" Or Herod, "Look at me! My family built this awesome temple! We're awesome! I'm the king!"
We all want to be the kings of our worlds. We want to convince God that we are keepers of the Law. After all, who would own up to hating God and hating others? But that's what we've been learning all week. Jesus came to save those who are nothing, have nothing, and can give nothing.
Jesus came to save us by being what we needed. Since the Law shows we don't love God with all our hearts, He did. Since the Law shows we don't love those around us, Jesus did. Since the Law says we should be damned for our disobedience, He was. In everything, Jesus by His life, death, and resurrection, is our Savior. He is our standing before God. He is our righteousness and our holiness.
And His salvation rescues us from that leaven of the Pharisees and Herod. He rescues us from trying to come up with some reason God should love us. He rescues us from trying to justify ourselves and claim credit for what the Lord gives us. Indeed, through our baptism into Christ, through His Word, through His Supper, He gives to us His very Self, the True Bread which gives us everlasting life.
While the doctrines of the Pharisees puffed them up, Jesus lifts us up in true honor and majesty, which comes not from ourselves but from Him. He gives Himself up for your sake and in His exaltation, He brings you along, too! In the Name + of Jesus. Amen.
O let Your mighty love prevail To purge us of our pride That we may stand before Your throne By mercy purified. (O Christ, Our Hope, Our Hearts' Desire, LSB 553:4)