A teaching of Jesus' during The Sermon on the Mount
This follows on from the charity teachings: Do not make a big show of your faith, everyone seeing you worship does not make you more devout or faithful. Simple Prayer in private means that you feel things more in your heart, and God will notice that.
This gives voice to a problem I have with... "vocal" Christians. The people who will go on TV and shout and scream about divine revenge and absolutions. It's wrong to do so, but I wonder at their motives for this.