take an oath
To make a formal, binding promise (to do something). You took an oath when you agreed to be a witness in this trial, so you must answer my questions completely truthfully! We all took oaths to keep this a secret until the day we die.
take an oath
to make an oath; to swear to something. You must take an oath that you will never tell anyone about this. When I was a witness in court, I had to take an oath that I would tell the truth.
take an oath
To agree to a pledge of truthfulness or faithful performance.