Book of Judgments

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) sent Sayyiduna Ali (may Allah be pleased with him) to Yemen and said: "Teach them the rulings of the Shari'ah and judge between them." He said: I have no knowledge of judging. So he (peace and blessings be upon him) struck his chest with his hand and supplicated: 'Allahumma ihdihi al-qada'' (O Allah, guide him and grant him understanding in judging).
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.

It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that two men brought their dispute to the Prophet (peace and blessings be upon him). He (peace and blessings be upon him) said to Sayyiduna Amr bin al-As: "You judge between them." He said: O Messenger of Allah! Shall I judge in your presence? He said: "Yes, on the condition that if you judge correctly, you will have ten rewards, and if you strive (make ijtihad) but err, you will have one reward."
This hadith is sahih al-isnad (authentic in its chain), but the two Shaykhs did not record it with this wording.