Do not easily believe evil of another, particularly a brother or sister in Christ. Never repeat something bad about someone else that you do not know to be true. Breaking a promise is a form of lying. When you say you are going to do something, you must make it good. Stand up for others and vindicate them when they are injured by lying lips.
Silence is consent.
Jonathan spoke in David's defense, knowing that what Saul said about him was slanderous. Oaths are solemn declarations that invoke God as a witness of one's statements and promises. And do not swear by your head, for you cannot make even one hair white or black. Jesus himself submitted to an oath at his trial recorded in Mt 26. In verse 62, he is silent.