Sayyiduna Mu'adh (may Allah be pleased with him) said: Two men insulted each other in the presence of the Prophet (peace and blessings be upon him), and one of them became angry. He (peace and blessings be upon him) said: "I know a word which, if he were to say it, his anger would go away: 'A'udhu billahi min al-shaytan al-rajim' (I seek refuge in Allah from Satan, the accursed)."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17424