The phrase "trust the source" means to have confidence in the reliability, accuracy and credibility of a particular information or data that comes from a specific person or organization. It implies that you believe what you are being told because it is coming from someone who has proven themselves to be truthful, honest and dependable. In other words, trusting the source means putting your faith in the integrity of the provider of information, believing that they have your best interests at heart and will not intentionally mislead or deceive you.