Musnad Ahmad 541:21

'Affan narrated to us, [saying] Aswad ibn Shayban narrated to us, [saying] Abu Nawfal ibn Abi 'Aqrab narrated to us, saying: 'Amr ibn al-'As became extremely anxious at the time of death. When his son, 'Abdullah ibn 'Amr, saw that, he said: "O Abu 'Abdullah, what is this anxiety, when the Messenger of Allah (may Allah bless him and grant him peace) used to bring you close and employ you?" He said: "O my son, that was indeed the case, and I will tell you about that. By Allah, I do not know if that was out of love, or if he was reconciling me [to Islam]. But I bear witness regarding two men that he departed this world while he loved them: the son of Sumayyah and the son of Umm 'Abd." When he told him this, he placed his hand on the place of the beard on his chin and said: "O Allah, You commanded us, and we neglected; You forbade us, and we committed; and nothing can encompass us except Your forgiveness." That remained his constant refrain until he died.