trust, but verify
It is acceptable to trust someone or something, as long as their or its trustworthiness or veracity is confirmed. The phrase comes from a Russian proverb and was popularized by US President Ronald Reagan. A: "I want to believe her, and I don't want to offend her, but ultimately I'm skeptical." B: "Trust, but verify. Make a phone call to confirm what she's saying is true."
verify something with someone
to check with someone to make sure that something is the truth. I will have to verify your story with the storekeeper. I verified your story with the other witness.