In standard English usage, the verb say can have as its object either a literal utterance, a noun phrase, or a subordinate clause. But even in the last two cases, the object must refer to at least a figurative utterance. Four examples:
1. He glanced up and said, "No thank you." [an utterance]
2. She lowered her head and said grace. [a noun phrase]
3. He says that he'll do it. [a subordinate clause]
4. Her facial expression said she was fed up.
In example 4 the object is a subordinate clause (with the conjunction that left out). And the utterance is only figurative: Her facial expression conveyed her exasperation as though it could speak, and if so it would say, "I'm fed up."
When it comes, as in your example, to expressing the opinion that someone is smart, the closest might be things like
We declare him to be smart.
We proclaim him to be smart.
But each of those has at least a suggestion of a speech act