“Do not become angry.”

Abu Hurayrah (may Allah be pleased with him) reported: A man came to the Prophet (may Allah's peace and blessings be upon him) and said: "Advise me." He said: "Do not get angry." He repeated that several times, and every time, he would say: "Do not get angry."

Narrated by Abu Hurayrah and recorded by al-Bukhari. A man asked for advice and was told this; he asked again, and again, and each time got the same three words and nothing else. The scholars read the repetition as the teaching — not that anger is the only fault, but that for this man, and for most people, everything else was downstream of it.