Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that Ali bin Abi Talib passed by the insane woman of such-and-such tribe who had committed fornication, and Umar bin al-Khattab (may Allah be pleased with him) had ordered her to be stoned. Sayyiduna Ali (may Allah be pleased with him) sent her back and said to Sayyiduna Umar: "O Commander of the Believers, will you stone her?" He said: "Yes." Sayyiduna Ali said: "Do you not remember that the Messenger of Allah (peace and blessings be upon him) said: 'The pen has been lifted from three: from the insane person whose mind is overpowered, from the sleeper until he wakes up, and from the child until he reaches puberty'?" Sayyiduna Umar said: "You have spoken the truth," and he let her go. This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.