A man who heard Sayyiduna Ali (may Allah be pleased with him) reports that he said: When the Messenger of Allah (peace and blessings be upon him) sent me to Yemen, I said: O Messenger of Allah (peace and blessings be upon him), you are sending me while I am a young man, and I have no knowledge of much of judging. He says: The Messenger of Allah (peace and blessings be upon him) struck my chest with his hand and said: "Allah will keep your tongue firm and guide your heart." After that, I never faced any difficulty in judging between two people.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النذور / 20155