What is the dividing line between God's will and human choice in divine decree and destiny?

Predestination is Allah Almighty's secret in His creation; no close angel nor sent prophet was given knowledge of it. The Prophet, peace and blessings be upon him, forbade delving into it because it is a pitfall for feet and a迷 for understandings. Belief in predestination is a pillar of faith, and a Muslim must know that Allah encompasses all things with His knowledge, and everything that happens in the universe is by His will. What befell him could not have missed him, and what missed him could not have befallen him. A servant's choice of things is by Allah Almighty's will, knowledge, and power, as He Almighty said: "And you do not will except that Allah wills." Therefore, a Muslim should not involve himself in delving into matters that his mind cannot comprehend.