Why did God create evil and Satan, and is there a clear answer to that in the Qur'an or Sunnah?

God's creation of Iblis contains great wisdoms and immense benefits, among them:

1. The completion of the ranks of servitude for His prophets and saints through their struggle against Iblis and his party, which results in tremendous worldly and otherworldly benefits. 2. The fear of angels and believers of sin after witnessing the state of Iblis and his fall, which achieves greater servitude and submission to God. 3. Making him an example for anyone who disobeys His command, becomes arrogant, and persists in sin. 4. His being a test by which the evil among His creation is distinguished from the good, thereby demonstrating the diversity in their original matter. 5. Manifesting the perfection of God's power in creating opposites, such as Jibreel and Iblis, which reflects the greatness of His will and sovereignty. 6. Demonstrating the beauty of an opposite through its opposite; for without the ugly, the virtue of the beautiful would not be known. 7. Achieving various types of gratitude to God, as His saints, by their gratitude to God for the existence of Iblis and their trial by him, attained what would not have been achieved without him. 8. Achieving beloved servitudes to God such as love, repentance, reliance on God, patience, and contentment, which become manifest through the struggle against Iblis and his party. 9. Manifesting the wonders of God's power and the subtleties of His creation through the existence of those who oppose His messengers and disbelieve them. 10. The manifestation of His wisdom and power from the fiery and earthly materials from which He created, showing the diversity of His creation. 11. Manifesting the implications of God's names and attributes such as "The Abaser, The Exalter, The Honorer, The Humiliator, The Judge, The Just, The Avenger." 12. Demonstrating the complete dominion of God through the diversity of His actions, from reward and punishment to honoring and humiliating. 13. His wisdom necessitating the creation of opposites and placing everything in its proper place, which completes wisdom and power. 14. Completing praise for God in all aspects; He is praised for His justice and withholding just as He is praised for His bounty and giving. 15. Manifesting His forbearance, patience, vast mercy, and generosity, despite His creation's disobedience to Him.

These wisdoms and benefits highlight the perfection of His praise, wisdom, and power. The existence of this creature — even though he is hated — results in countless beloved things for God Almighty, and indicates that His wisdom has reached as far as His power has reached.