It is narrated from Qadi Shurayh that Sayyiduna Umar bin Al-Khattab, may Allah be pleased with him, wrote to him: If a matter comes to you which is found in the Noble Qur'an, then decide according to it, and do not turn to people's (opinions). And if a matter comes to you which is not in the Book of Allah, then look to the Sunnah of the Messenger of Allah, peace and blessings be upon him, and decide according to it. And if such a matter comes before you in which there is no guidance in the Book of Allah or the Sunnah of the Messenger of Allah, peace and blessings be upon him, then look at the consensus of the people regarding it and adopt that. And if an issue arises which is neither in the Book of Allah, nor in the Sunnah of the Messenger of Allah, peace and blessings be upon him, nor has anyone before you said anything about it, then choose one of two things: if you wish, exercise ijtihad and express your opinion, and if you wish, refrain. And I consider refraining to be better for you.