How do we know that God knows our thoughts and actions?

In Genesis 18, the interaction between God and Sarah reveals the profound truth of God's omniscience. When Sarah laughs at the promise of bearing a son, God not only hears her laughter but also confronts her directly, demonstrating His complete knowledge of her heart and mind. This is essential to understanding the nature of God; He sees beyond our outward actions to our innermost thoughts. Recognizing God's omniscience invites Christians to live with sincerity and honesty before Him, understanding that pretenses are futile. Psalm 139 also reflects this beautifully, conveying that God knows our thoughts even before we speak.