Musnad Ahmad 25:911

Husayn narrated to us, Dawayd narrated to us, from Salam ibn Bashir, from Ikrimah, from Ibn Abbas, who said: The Prophet, peace and blessings of Allah be upon him, said: "Two believers met at the gate of Paradise: a wealthy believer and a poor believer who were [as such] in the world. The poor one was admitted into Paradise, and the wealthy one was detained for as long as Allah willed that he be detained. Then he was admitted into Paradise, and the poor one met him and said: 'O my brother, what detained you? By Allah, you were detained until I feared for you.' He said: 'O my brother, I was detained after you for a terrible, hateful detention. I did not reach you until there flowed from me of sweat that which, if one thousand camels—all of which eat salt-bushes—were to come to it to drink, they would have departed from it fully quenched.'"