On the road to Damascus, what flashed around Saul before he fell to the ground?

Answer: A light from heaven

A light from heaven flashed around Saul; he fell to the ground and heard a voice say, "Saul, Saul, why do you persecute Me?"

“As Saul drew near to Damascus on his journey, suddenly a light from heaven flashed around him. He fell to the ground and heard a voice say to him, “Saul, Saul, why do you persecute Me?””— Acts 9:3-4 (BSB)