Musnad Ahmad 26:112

Yahya narrated to us, from Shu'bah, 'Amr ibn Murrah narrated to me, from 'Abdullah ibn Salamah, who said: 'Abdullah said: "Your Prophet, may Allah bless him and grant him peace, was given the keys to everything except five: {Indeed, Allah [alone] has knowledge of the Hour and sends down the rain and knows what is in the wombs. And no soul perceives what it will earn tomorrow, and no soul perceives in what land it will die. Indeed, Allah is Knowing and Acquainted} [Luqman: 34]."