The Maliki scholar Al-Qurtubi states, "their punishment in case of non-payment jizya while they were able do so is permitted; however, if their inability to pay it was clear then it isn't lawful to punish them, since, if one isn't able to pay the jizya, then he is exempted". According to Abu Yusuf, jurist of the fifth Abbasid Caliph Harun al-Rashid, those who didn't pay jizya should be imprisoned and not be let out of custody until payment; however, the collectors of the jizya were instructed to show leniency and avoid corporal punishment in case of non-payment. If someone had agreed to pay jizya, leaving Muslim territory for enemy land was, in theory, punishable by enslavement if they were ever captured. This punishment did not apply if the person had suffered injustices from Muslims.