The basic prerequisite for issuing fatwas under the classical legal theory was religious knowledge and piety. According to the "adab al-mufti" manuals, a mufti must be an adult, Muslim, trusted and reliable, of good character and sound mind, an alert and rigorous thinker, trained as a jurist, and not a sinner. On a practical level, the stature of muftis derived from their reputation for scholarly expertise and upright character. Issuing of fatwas was among the most demanding occupations in medieval Islam and muftis were among the best educated religious scholars of their time.