courage of one's convictions, have the - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Behave according to one's beliefs. For example, Carl wouldn't give his best friend any of the test answers; he had the courage of his convictions. This expression is believed to have originated as a translation of the French le courage de son opinion (“the courage of his opinion”), dating from the mid-1800s and at first so used. By the late 1800s it had changed to the present form.