The Prophet (saas) revealed that only Allah can know the unseen

the word "ghaib" in the qur'an is used for hidden things that man cannot see or know. things that will happen in the future are unknown to us, for instance. yet everything to do with the future, the future of every individual, country, building and piece of furniture, is known to allah. this is how the prophet (saas) was told to explain that knowledge of the invisible (ilm-ul-ghaib) lies solely with allah:

say: "allah knows best how long they stayed. the unseen of the heavens and the earth belongs to him. how perfectly he sees, how well he hears! they have no protector apart from him. nor does he share his rule with anyone." (surat al-kahf: 26)

say: "no one in the heavens and the earth knows the unseen except allah." they are not aware of when they will be raised. (surat an-naml: 65)

say: "my lord hurls forth the truth-the knower of all unseen things." (surah saba': 48)

in the qur'an, the prophet (saas) is commanded thus:

say: "i possess no power to help or harm myself, except as allah wills. if i had had knowledge of the unseen, i would have sought to gain much good and no evil would have touched me. i am only a warner and a bringer of good news to people who believe." (surat al-a'raf: 188)