Musnad Ahmad 1147:1

Yahya ibn Ishaq narrated to us, Layth ibn Sa’d informed us, from Yazid ibn Abi Habib, from Suwayd ibn Qays, from Zuhayr ibn Qays al-Balawi, from Alqamah ibn Ramthah: That the Messenger of Allah, peace and blessings of Allah be upon him, sent ‘Amr ibn al-‘As to Bahrain. The Messenger of Allah, peace and blessings of Allah be upon him, went out on an expedition, and we went out with him. The Messenger of Allah, peace and blessings of Allah be upon him, became drowsy and said: "May Allah have mercy on ‘Amr." He said: So we discussed everyone whose name was ‘Amr. He said: Then the Messenger of Allah, peace and blessings of Allah be upon him, became drowsy and said: "May Allah have mercy on ‘Amr." He said: Then he became drowsy a third time, and he woke up and said: "May Allah have mercy on ‘Amr." We said: "O Messenger of Allah, which ‘Amr is this?" He said: "‘Amr ibn al-‘As." We said: "And what is his affair?" He said: "Whenever I would call the people to charity, he would come and give generously from it. I would say: 'O ‘Amr, from where did you get this?' He would say: 'From Allah.' And ‘Amr spoke the truth; indeed, he has much good with Allah." Zuhayr ibn Qays said: When the Messenger of Allah, peace and blessings of Allah be upon him, passed away, I said: "I will surely stick to this man whom the Messenger of Allah, peace and blessings of Allah be upon him, said: 'Indeed, he has much good with Allah,' until I die."