You can't endanger your salvation based on the words that you say. On the contrary, your words indicate where your heart is. I found this Bible commentary:

http://biblehub.com/commentaries/matthew/12-37.htm

...men are said to be justified by faith (Romans 3:28 et al.), justified by works (James 2:24), justified—as here—by words. All three—faith, works, words—are alike elements of a man’s character, making or showing what he is.

Jesus wasn't a master of words. Jesus had the power to heal. Jesus could heal without words. Nobody has been able to do that since the first century apostles died.