Caution helps when supported by a real reason. For instance, if ownership of a particular item is genuinely unclear and a legitimate alternative exists, verify the facts or choose the clearer transaction.
By contrast, constantly suspecting people’s motives without evidence or repeatedly questioning ordinary permitted activities is not the intended principle. Ask qualified people where clarification is needed, then act on a reliable answer.
يَرِيبُكَ is a present-tense verb meaning “causes you doubt.” لَا يَرِيبُكَ negates the same verb. The parallel phrases make the contrast clear.