David’s Offer to Fight
1 Samuel 17: 32-39
1Sa 17:32 And David said to Saul, “Let no man's heart fail because of him. Your servant will go and fight with this Philistine.”
1Sa 17:33 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.”
1Sa 17:34 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,
1Sa 17:35 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.
1Sa 17:36 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.”
1Sa 17:37 And David said, “The LORD who delivered me from the paw of the lion and from the paw of the bear will deliver me from the hand of this Philistine.” And Saul said to David, “Go, and the LORD be with you!”
1Sa 17:38 Then Saul clothed David with his armor. He put a helmet of bronze on his head and clothed him with a coat of mail,
1Sa 17:39 and David strapped his sword over his armor. And he tried in vain to go, for he had not tested them. Then David said to Saul, “I cannot go with these, for I have not tested them.” So David put them off.

Union Gospel Press
Believers Bible Commentary
esword.com
John Wesley
Matthew Henry Concise Commentary
Matthew Henry Commentary
Robert Hawker
https://www.biblestudytools.com/commentaries/matthew-henry-complete/
http://www.bible-studys.org/index