What is the wisdom behind God's creation of animals we do not eat, such as snakes, scorpions, and rats?

Allah created harmful animals for general and specific wisdoms. The general wisdom is for the Muslim to believe that Allah is All-Wise and does not create anything in vain. As for the specific wisdoms, they include: demonstrating the perfection of His creation and His management; testing His servants; revealing man's weakness and helplessness; distinguishing between what is beneficial and what is harmful; extracting beneficial medicines from them; forming a link in the ecological balance; and affirming that all of His actions are good, and there is no pure evil in His creations.