What is the wisdom behind Allah Almighty leaving Satan to deceive and mislead people, instead of punishing him immediately and deferring that until the Day of Resurrection?

Summary of the Answer: It is obligatory to believe that all of Allah the Almighty's actions are based on profound wisdom, whether apparent or not, and not merely on His will. Questioning the wisdom of Allah's actions out of opposition is not permissible. However, questioning with the intent of seeking knowledge and increasing certainty is permissible.

Among the wisdoms behind the existence of Iblis and his temptation of humanity are: 1. Testing humans and distinguishing the wicked from the good, and holding each soul accountable for its deeds. 2. Completing the stages of servitude for prophets and saints by striving against Satan and seeking refuge in Allah from him. 3. Achieving the virtues of patience, perseverance, and striving that result from resisting Iblis's whispers. 4. Manifesting Allah the Almighty's attributes such as forbearance, wisdom, forgiveness, and pardon towards those who fall into sin.

For more details, one may refer to the book "Shifa' al-Alil fi Masa'il al-Qada' wa al-Qadar (definition) wa al-Hikmah wa al-Ta'lil" by Ibn al-Qayyim.