Musnad Ahmad 30:3571

Rawh narrated to us, Malik narrated to us, from Ibn Shihab, from Sa'id ibn al-Musayyib, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The strong one is not the one who throws others down; rather, the strong one is the one who controls himself when angry."