Musnad Abi Ya'la 587 — Abu Zabyan (may Allah have mercy on him)

Abu Zabyan (may Allah have mercy on him) relates that a woman who had committed adultery was brought to Sayyiduna Umar (may Allah be pleased with him), and he ordered that she be stoned. Then, when she was taken past Sayyiduna Ali (may Allah be pleased with him), he recognised her and set her free. So Sayyiduna Umar (may Allah be pleased with him) was informed: "Ali (may Allah be pleased with him) has taken her from our hands and released her." He said: "Call him to me." When he came, Sayyiduna Umar (may Allah be pleased with him) asked: "Why did you release her?" Sayyiduna Ali (may Allah be pleased with him) replied: "O Commander of the Believers, by Allah, you know well that the Messenger of Allah (peace and blessings be upon him) said: 'The pen (of accountability) has been lifted from three: from the sleeper until he wakes up, from the child until he reaches puberty, and from the insane until he recovers.' And the fact is that this is the insane woman of such-and-such a tribe, and most likely the one who did this act with her came to her while she was in that state of her mental affliction and illness."