Abdullah bin Amr's taking part in the Battle of Siffin at his father's command

Umar bin Shu'ayb narrates from his father, from his grandfather, that the mother of Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) used to treat the Prophet (peace and blessings be upon him) with great devotion and courtesy. One day he (peace and blessings be upon him) came to her and asked: "O Umm Abdullah! How are you?" She said: "I am well, O Messenger of Allah! May my father and mother be ransomed for you, how are you?" He (peace and blessings be upon him) asked: "And how is Abdullah?" She said: "He too is well." Abdullah was a man who had turned away from the world. On the day of Siffin, his father said to him: "Go out and fight." He said: "O my father! How can you order me to fight when you have heard the instruction of the Messenger of Allah (peace and blessings be upon him) that I heard?" His father said: "I ask you by Allah, do you not know that the Messenger of Allah (peace and blessings be upon him) took your hand, placed it in my hand and said: 'Obey your father, Amr bin al-As'?" He said: "Yes." His father said: "Then I order you to fight." So he went out to fight. When the war was over, Abdullah said in verse that had even a she-camel witnessed my stand and the scene at Siffin that day, its locks would have turned white; that evening when the people of Iraq came like spring clouds driven by the southern winds; whenever I said they had turned and fled, fresh battalions of theirs came before us and stood firm; they said to us: our view is that you pledge allegiance to Ali, and we said: our view is that you should be fought.

It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that he said: We were with the Messenger of Allah (peace and blessings be upon him) on one of his campaigns when the people were suddenly alarmed. I went out wearing my weapons and saw Sayyiduna Salim (may Allah be pleased with him), the freed slave of Abu Hudhayfah, also wearing his weapons and walking with dignity and calm. I said to myself: I will certainly follow the example of this righteous man. Eventually he went and sat at the door of the Messenger of Allah (peace and blessings be upon him), and I sat with him. Then the Messenger of Allah (peace and blessings be upon him) came out in a state of anger and said: "O people! What is this haste and what is this agitation? Were you unable to do as these two believing men did?"
This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.

Amr bin Qays al-Sakuni states: I was with my father at Huwwarin when a man approached. When the people saw him, they rushed towards him, and I was among those who rushed to his gathering. I asked: Who is this person? The people told me: This is Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both).

It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that he said: I said: O Messenger of Allah! Do you permit me to write down everything I hear from you? He (peace and blessings be upon him) said: "Yes." I said: Shall I write in (both states of) pleasure and anger? He (peace and blessings be upon him) said: "Yes, for it is not fitting that I should say anything but the truth, whether in pleasure or in anger."
This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.