The translator can state more clearly the implied reason about why we should believe what God says: Alternate translation: "If we believe what people say, then we should believe what God says because he always tells the truth" (See: [[rc://en/ta/man/translate/figs-explicit]])
The idiom to "receive the witness" means to believe what another person testifies concerning something that he has seen. The abstract noun "witness" can be translated with a verbal phrase. Alternate translation: "believe what men testify" or "believe what men say about what they have seen" (See: [[rc://en/ta/man/translate/figs-idiom]] and [[rc://en/ta/man/translate/figs-abstractnouns]])