bismilah was salat wassalam ala khairil anaam.

When rasululah (saw) sent muadh bin jabal ra to govern yemen he asked him oh muaz! How will you solve the problems of the people? He replied through the book of allah swt. The prophet pbuh then askd what if u dont find the answer in the quran? He replied i will look into your beloved practices (sunnah). The prophet pbuh then asked what if u dont find it in my sunnah? He replied i will do ijtihad. The prophet pbuh then thanked allah swt for giving such an answer from which he pbuh was pleased (abu dawud, tirmizy) Hafiz ibn qayim ra has stated this hadith is not only sahih but mashoor also.