Idris al-Awdi (may Allah have mercy on him) said that Sa'id bin Abi Burdah (may Allah have mercy on him) brought out a letter before us and said: This is the letter of Umar (may Allah be pleased with him) to Abu Musa (may Allah be pleased with him); in it is written: "Beware of distress, of harming people, and of quarrels in the places of truth, through which Allah establishes reward and lays up a store for the servant. Whoever keeps his inner self sound and upright before Allah, Allah sets right the affairs between him and people. And whoever adorns himself before people with what Allah knows to be contrary to his reality, Allah disgraces him. So what do you think of the reward of other than Allah in the quick gains of this world, compared with the treasuries of His mercy? And peace."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20283