Biblical explanation
God is repeatedly presented as uniquely knowing the human heart. 1 Kings 8:39 says: "thou, even thou only, knowest the hearts of all the children of men." Psalm 139 describes God's complete knowledge of a person's thoughts and words. Scripture never attributes this unlimited knowledge of human hearts to Satan. Satan can observe human behavior and circumstances. In the book of Job, Satan makes claims based on what he observes about Job's situation (Job 1:9-11). Satan also tempted Jesus after observing His circumstances and fasting (Matthew 4:1-11). There is no biblical statement saying that Satan can read everyone's thoughts. Therefore, Christians should not live in fear that Satan possesses the same kind of unlimited knowledge that belongs to God. God alone is omniscient. Satan is a powerful creature, not God.
Key takeaway
Discipleship applies the gospel to the whole life: body, mind, relationships, work, finances, and worship. Healthy choices and faithful habits do not earn salvation; they are grateful stewardship of the life God has entrusted to us and practical ways to serve others.