1 Samuel 17:31-36

When the words which David spoke were heard, they told them to Saul, and he sent for him. David said to Saul, “Let no man’s heart fail on account of him; your servant will go and fight with this Philistine.” Then Saul said to David, “You are not able to go against this Philistine to fight with him; for you are but a youth while he has been a warrior from his youth.” But David said to Saul, “Your servant was tending his father’s sheep. When a lion or a bear came and took a lamb from the flock, I went out after him and attacked him, and rescued it from his mouth; and when he rose up against me, I seized him by his beard and struck him and killed him. Your servant has killed both the lion and the bear; and this uncircumcised Philistine will be like one of them, since he has taunted the armies of the living God.”