What is the ruling on a human claiming to be an angel, and can angels have relative knowledge of the unseen?

If a person intends to resemble the angels in obedience and avoidance of sin, it is not permissible, because it involves self-praise (tazkiyat al-nafs), as Allah Almighty says: "So do not praise yourselves; He is most knowing of who is righteous." (An-Najm: 32). However, if one claims to be an actual angel—and is not mentally incapacitated—this is a forbidden lie and slander, as Allah Almighty says: "Indeed, Allah does not guide one who is a transgressor and a liar" (Ghafir: 28), and His saying: "Indeed, those who invent falsehood about Allah will not succeed" (Yunus: 69). Angels do not know the unseen except for what Allah reveals to them, as Allah Almighty says: "Knower of the unseen, and He does not disclose His [knowledge of the] unseen to anyone Except whom He has approved of messengers" (Al-Jinn: 26-27).