The beard!
(Martin Luther)
"I know that nothing good lives in me, that is, in my sinful nature. For I have the desire to do what is good, but I cannot carry it out!" Romans 7:18
Sin in us, is like the beard. We are shaved today and look clean, and have a smooth chin. Tomorrow our beard has grown again - nor does it cease growing while we remain on earth. In like manner sin cannot be extirpated from us; it springs up in us as long as we live!
"Oh what a wretched man I am! Who will free me from this life that is dominated by sin and death!" Romans 7:24