Some mentors fix themselves in our memory.  Most people remember the name of their reception class teacher.  After that the kind or the cruel are impressed somewhere on our brain, but especially those people who helped our learning leap forward.  We recall them, partly by their ability to convey information, but more by their character, their enthusiasm for their subject and their personal interest that we should do extremely well in the subject - because they have personally put everything into it.  Paul was that kind of teacher.  His life was devoted to pleasing Jesus well, and so it mattered to him that his students excelled too (1 Corinthians 11:1).  And the Holy Spirit enabled him to know and communicate life-changing truth from Jesus Christ (1 Corinthians 2:13).

Here Paul reminded them of the essential change-process: you cannot live a new life without first renouncing the old.  A problem for many Christians is that they try to integrate the two.  It never works!  The old nature is riddled with corruption and so easily re-contaminates us (Romans 7:5).  Given half a chance it will be back to its old ways - which is why it needs to be discarded as definitely as rancid food.  

This choice is set before us by faithful teachers of God's Word.  But teaching is not enough, even if we agree with it.  We have the responsibility to choose to obey.  The decision to put off the old nature is made in the mind, but it has to have the full agreement of the heart: you will only follow the decision through because it is the thing you really want to do.  Colossians 3:8-10 underlines today's verses, "But now you must also rid yourselves of all such things as these: anger, rage, malice, slander, and filthy language from your lips. Do not lie to each other, since you have taken off your old self with its practices and have put on the new self, which is being renewed in knowledge in the image of its Creator."

Compared with the indelibly stained old nature, God's righteous and holy nature is a blast of fresh air. It may even be somewhat overwhelming, at first, to be given His Word and to realise that He intends to fill us with His Holy Spirit so that we can put on a new nature, just like His.  Again, this has to be an active choice - fuelled by a desire to be pleasing to God in every way and determined to do whatever is necessary to ensure that we are.  The workplace is a better test-bed for this new nature than most realise.  Christians who are wise will not seek worldly approval at work while attracting spiritual admiration at church.  We only have one life - the Christian life.  So, let the office, factory, farm, school, shop or hospital see that you have renounced corruption (in its many forms) and have fully embraced Jesus Christ.