Morality without command or revelation from the Creator

peace.
In your opinion, without the principled statement of "and do what is right and good" (and assuming that this statement deals with the moral commandment), would there be any reason to expect a person to behave according to morality?
And we would say: (a) If so. Yes, man has reason, and through it we expect him to behave morally. If so, why was this fundamental verse written (and does it not add a layer of 'commandment'? There is no commandment here to break a commandment and to nullify an act, etc.)? It is unnecessary! Proof of this can be provided from God's observation not to murder in the Bible, even though there was no commandment at that time. (b) If not. Yes, the rational system is not a tool for producing a moral act (but only a descriptive one). And in order to produce a motive for action, a direct command from the Creator is needed. If so, why did the Creator not command this explicitly (and not just 'and you did', which is not included in the list of commandments)? Beyond that, why did the Creator expect that they would not be murdered, and why did He not command, and did not even reveal it ('and you did')!