Musannaf Ibn Abi Shayba 33:867

'Affan narrated to us, he said: Juwayriyah ibn Asma' narrated to us, from Isma'il ibn Abi Hakim, who said: 'Umar ibn 'Abd al-'Aziz became angry one day, and his anger intensified, and there was sharpness in him, and 'Abd al-Malik, his son, was present. When they saw that his anger had subsided, he said: "O Commander of the Faithful, you are in the measure of Allah's favor upon you, and in the position in which Allah has placed you, and with what Allah has entrusted you of the affairs of His servants—does anger reach you to the extent that I see?" He said: "How did you say?" So he repeated his words to him. He said: "Do you not get angry, O 'Abd al-Malik?" He said: "What would the vastness of my interior avail me if I did not restrain anger within it, until nothing of it appears that I would dislike?"