Musannaf Ibn Abi Shayba 28:383

Waki’ narrated to us, from al-A’mash, from Abu Wa’il, from Masruq, from ‘Aisha, who said: When Abu Bakr fell ill with the illness from which he died, he said: "Look at what has increased in my wealth since I entered the position of leadership, and send it to the Caliph after me; for I had been considering it lawful for myself, and I used to consume of the fat [provisions] an amount similar to what I used to obtain in trade." She said: When he died, we looked, and there was a Nubian slave who used to carry the children, and there was a camel used for drawing water that he used to irrigate with. So we sent them both to ‘Umar. She said: My grandfather—meaning my agent—informed me that ‘Umar wept and said: "May the mercy of Allah be upon Abu Bakr; he has truly exhausted those who come after him with a severe exhaustion."