Is it valid to attribute knowledge of the Unseen to the righteous, and is it possible for any human to discover the unseen after the cessation of revelation?

It is not permissible to attribute knowledge of the unseen to anyone other than Allah the Almighty. Whoever does so disbelieves in what was revealed to Muhammad, peace be upon him, for Allah the Almighty says: "Say: None in the heavens and earth knows the unseen except Allah." Indeed, Allah has reserved knowledge of the unseen exclusively for Himself, and He has not disclosed it to anyone except the messengers whom He chose. The message was concluded with Muhammad, peace be upon him, whom Allah commanded to say: "Say: I do not tell you that I have the treasures of Allah, nor do I know the unseen." Whoever attributes knowledge of the unseen to anyone must repent and re-examine their belief.