I love this.  I think the unique experience of teaching God's Word unlocks insight that cannot be gleaned -- at least not as powerfully -- simply by listening to someone else's teaching.

Or to say it another way, when you actually teach something to someone else from God's Word, the Holy Spirit will take your own words and run a "systems check" in your heart without your conscious knowledge, and if something in there contradicts your own words, He'll bring it to your remembrance.  Then, as you're speaking God's Truth into someone else's life, God will also bring you to the point where you have to deal with your own sin with Him, either asking forgiveness for the sin yet unconfessed, or asking Him to help you completely turn from that thing you have been unable to turn from yet.

This is one reason why I love teaching the Word: when you do so, God won't let you even pretend you're getting away with anything.  I am -- "naturally" or "flesh" speaking -- someone who can get into trouble when left to my own devices.  Anyone else out there like me?  Those of you who didn't raise your hands need to ask forgiveness for your fib. :)

But when I study in preparation and then stand up to teach and speak forth the Truth of God's Word, the Lord will call to my remembrance things that I had either run from (rather than confessed) or forgotten about, and then uses my own words to show me "see, you know these things are wrong, so now you also know you have no excuse...time to deal with them, son."

You have to honestly, genuinely, actively *TRY* to teach the Word and still live in sin -- it's not something that can "just happen" (though that's always what we tell people), nor is it something where "God's okay with it". If you are His child, He *WILL* bring these things to your remembrance when you teach them to others, and He will trouble your soul with them until you deal with them.