What did Saul conclude when he saw the light coming from above?
Saul concluded that his God, the God of Abraham, Isaac, and Jacob, was dealing with him. Seeing the penetrating light from above, he instinctively recognized a heavenly source, addressed it as Lord, and asked, "Who art thou, Lord?" This was his conclusion.
Les explains that God in grace did not wait for Saul to have second thoughts or to question his overzealousness. Saul remained intent on arresting believing Jews, even from Damascus, whether men, women, or children, to take them back to Jerusalem for prison or death. But God stopped him in his tracks with a penetrating light from heaven, which Les suggests knocked him from his horse. From his prostrate position on the ground, Saul looked up, knowing that shining light came from heaven. Since religious people normally think of God's abode as heaven above, Saul was no different. As he saw that light from above, second nature told him his God was dealing with him—the God of Abraham, Isaac and Jacob. So he asked, "Who art thou, Lord?"