It is narrated from Sayyiduna Sa'd bin Abi Waqqas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The supplication of Dhu al-Nun (Yunus, peace be upon him) which he made while he was in the belly of the fish: 'La ilaha illa anta subhanaka inni kuntu minaz-zalimin' ((O Allah,) there is no true god except You; You are free of all imperfection; indeed, I have been among the wrongdoers) [Surah al-Anbiya: 87] . The fact is that whenever any Muslim man supplicates with it in any matter at all, Allah Almighty certainly answers his supplication." This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.