It is narrated from Sayyiduna Jubayr bin Mut'im (may Allah be pleased with him) that a man came to the Prophet (peace and blessings be upon him) and said: O Messenger of Allah! Which part of the lands is the worst? He (peace and blessings be upon him) said: "I do not know." Then when Jibril (peace be upon him) came, he (peace and blessings be upon him) asked: "O Jibril! Which part of the places is the worst?" He said: I do not know until I ask my Lord. So Jibril (peace be upon him) went away and stayed as long as Allah willed, then came back and said: O Muhammad! You asked me which are the worst places, and I said that I did not know; then I asked my Lord which are the worst places, and Allah said: "Their markets." The two Shaykhs used all the narrators of this hadith as evidence except Abdullah bin Muhammad bin Aqil, while Imam Bukhari alone used Abu Hudhayfah as evidence; and this hadith is a basis (proof) for a scholar saying "I do not know".