When God wants us to perform a task for him and we need to use words, he is willing to change our language. Isaiah experienced this.
Our actions often speak louder than our words. Someone who claims something, but does not act accordingly, loses his credibility. Therefore, let our words and actions correspond.
We are called to profess our faith in Christ, without any shame.
When we speak about other people, we must speak the truth. Lying about the other is also called gossiping. Lying to deliberately harm the other is called a false witness.