Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: "Your Prophet (peace and blessings be upon him) was given the keys to everything, except for five things (which are mentioned in the Qur'an in these words): 'Indeed, with Allah Almighty is the knowledge of the Hour; He sends down the rain; He knows what is in the wombs; no soul knows what it will earn tomorrow; and no soul knows in which land it will die. Indeed, Allah Almighty is All-Knowing, All-Aware.'"
Imam Ahmad and Abu Ya'la recorded it, and the narrators of both are the narrators of the Sahih.