1 Samuel 17:31-36

When the words that David spoke were heard, they repeated them before Saul, and he sent for him. And David said to Saul, “Let no man’s heart fail because of him. Your servant will go and fight with this Philistine.” And Saul said to David, “You are not able to go against this Philistine to fight with him, for you are but a youth, and he has been a man of war from his youth.” But David said to Saul, “Your servant used to keep sheep for his father. And when there came a lion, or a bear, and took a lamb from the flock, I went after him and struck him and delivered it out of his mouth. And if he arose against me, I caught him by his beard and struck him and killed him. Your servant has struck down both lions and bears, and this uncircumcised Philistine shall be like one of them, for he has defied the armies of the living God.”