Riddle me this: The proper phrase to "refrain from speaking" is to "hold or keep one's PEACE," while the proper phrase to "express one's opinion" is to "speak one's PIECE."
Two idiosyncratic phrases that use homonyms meaning the same thing but spelled differently... thanks English.
14. Hold or keep one's peace, to refrain from or cease speaking; keep silent: He told her to hold her peace until he had finished.
33. Speak one's piece, to express one's opinion; reveal one's thoughts upon a subject: I decided to speak my piece whether they liked it or not.