The Forty Hadiths of al-Nawawi On the authority of Abu Muhammad al-Hasan ibn Ali ibn Abi Talib the grandson of the Messenger of Allah, peace be upon him, and his beloved flower may Allah be pleased with them both who said: I memorized from the Messenger of Allah, peace be upon him: "Leave that which makes you doubt for that which does not make you doubt." It was recorded by al-Tirmidhi and al-Nasa'i and al-Tirmidhi said it is a hasan sahih hadith. This hadith guides the Muslim toward a magnificent principle of conduct and faith, which is to abandon that which causes doubt and anxiety, and to turn toward that which brings tranquility to the soul. For the sincere believer distances himself from ambiguities and suspicious matters in order to preserve his religion and the peace of his heart. The hadith teaches that the purity of the heart and the excellence of piety are manifested in choosing what is clearly lawful and abandoning everything that might lead a person into the unlawful or cause him to fall into ambiguity.