Ephesians 4:25-32

Therefore, having put away falsehood, let each one of you speak the truth with his neighbor, for we are members one of another. Be angry and do not sin; do not let the sun go down on your anger, and give no opportunity to the devil. Let the thief no longer steal, but rather let him labor, doing honest work with his own hands, so that he may have something to share with anyone in need. Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear. And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption. Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you.

-Ephesians 4:25-32

This section directly follows Paul's words "to put off your old self", and "to put on the new self".  I think this section is focusing on the idea of putting off the old self.  So, what follows is a long list of a bunch of things that followers of Christ are to no longer do.  To cease from these things is what it means to be putting off our old selves.

The first thing is truthfulness.  Do not speak lies to your neighbor.  Paul makes it clear that this is important because "we are all members of one another".  This is probably pointing to the idea Paul mentioned earlier about being members of the same body.  If that's the case, the person we are not to lie to is our brothers in Christ.  It probably still stands that we are not to lie to anybody (including outside the body of Christ), but I think here Paul is focusing on our interactions with other followers of Jesus.

Next, we are not to sin in our anger.  I've heard that we can infer from this that it is possible to be angry and not to sin.  To be angry doesn't necessarily mean that you are currently sinning.  However, it is clear that we need to beware of sinning while we are angry.  This is made even clearer by the fact that Paul warns that anger can give the devil an opportunity in our lives.  One way to avoid this is to not stay angry for very long, or as Paul puts it, "do not let the sun go down on your anger".

Stealing is wrong, so we are told not to steal.  Paul encourages to rather do honest work.  The purpose of this is so that they can have something to share with the needy.  This is directly opposite stealing.  Instead of taking something that is not yours from someone else, you are to be prepared so you can graciously give to someone who needs what you have.

Our speech and talk is of concern as well.  What we say should not tear down, but instead should build up.  It is easy to hurt others with what we say.  Another thing that our mouths do is curse or use foul language.  The opposite of these things is building up, which is what we should instead be using our speech to do.  The purpose is to be a blessing to others, to build them up instead of tearing them down.

Lastly, there are all kinds of bad things (bitterness, wrath, anger, clamor, slander, malice) that we are not to have.  These things are part of what we put off.  What we put on instead is kindness, tenderheartedness, forgiveness.  With the encouragement of forgiveness, we are reminded that God in Christ forgave us.  We have received forgiveness, so we should also be forgiving to others.

Perhaps I was partly wrong in saying that this section focuses on the putting off.  It is partly true, but it seems that these things that Paul talks about us having to put off, he offers something we put on instead.  Perhaps the focus of what he is saying is what we put on instead, not really what we put off.  I think that's what Paul is encouraging his readers (and us).  Don't just avoid lying, but tell the truth since you are speaking truth to another member of the same body.  Don't just stop stealing, but work hard to have something to give someone in need.  Don't just stop saying bad things, but work on using your words to be an encouragement to others.  Though, this idea isn't quite as clear with what Paul says about anger, though it is still a good idea to avoid being angry for long.

I did miss out verse 30 and in a way perhaps this was good.  Perhaps the heart or guiding light of all of this is seeking to please God instead of grieving his Spirit.  How do we grieve the Holy Spirit?  The way that we live can grieve the Holy Spirit.  The push to please him is what should encourage us to speak the truth and build other up with our words.