Reason can rule over every desire; e.g, by reason, a habitual glutton or drunkard can learn a better way. A lover of money can learn to lend without interest to the needy and to cancel debts after seven years.
Reason rules the emotions for the law prevails in relationship with parents, one's wife, children, and friends. The law can prevail even over treatment of enemies and violent emotions; e.g., lust for power, arrogance, malice, and even anger.
In summary, "Now when God fashioned human beings, he planted in them emotions and inclinations, but at the same time he enthroned the mind among the senses as a sacred governor over all" (21-22).
The NISB cites Biblical references for the examples of law in this passage, including Gen 39:7-12; Ex 20:17; Ex 22:25; Lev 25:35-37; Deut 23:19-20; Det 15:1-3; Lev 19:9-10: Dt 20:19)