اجتهاد scriptural basis :: Remember, remember, the velvet November

Ma’adh said, according to the Quran. The Prophet thereupon asked what he would do if he did not find the solution to the problem in the Quran, to which Ma’adh said he would govern according to the Sunnah. But when the Prophet asked if he could not find it in the Sunnah also, Ma’adh said "ana ajtahidu" (I will exert myself to find the solution). The Prophet thereupon patted his back and told him he was right.