1 Samuel 17:37-39, 45-46
37 David said moreover, The Lord that delivered me out of the paw of the lion, and out of the paw of the bear, he will deliver me out of the hand of this Philistine. And Saul said unto David, Go, and the Lord be with thee.
38 And Saul armed David with his armour, and he put an helmet of brass upon his head; also he armed him with a coat of mail.
39 And David girded his sword upon his armour, and he assayed to go; for he had not proved it. And David said unto Saul, I cannot go with these; for I have not proved them. And David put them off him.
45 Then said David to the Philistine, Thou comest to me with a sword, and with a spear, and with a shield: but I come to thee in the name of the Lord of hosts, the God of the armies of Israel, whom thou hast defied.
46 This day will the Lord deliver thee into mine hand; and I will smite thee, and take thine head from thee; and I will give the carcases of the host of the Philistines this day unto the fowls of the air, and to the wild beasts of the earth; that all the earth may know that there is a God in Israel.
-After considering Saul’s gift of armor, David decided not to take it into battle because it hadn’t been proven. What’s important is that David still went to battle anyway, which tells us that David was relying on another armor that he had proven. Even though David was obedient to King Saul, David had already met with another King, a King of Kings, who had provided a special armor “not made with hands, that is to say, not of this building”. Saul couldn’t see it, the Hebrew army couldn’t see it, Goliath couldn’t see it; but David trusted that it would protect him just as it had previously against a lion and a bear. The Bible teaches that “if we faint in the day of adversity, our strength is small”. (Proverbs 24:10) So when trials come, do as David did and “take unto you the whole armour of God, that ye may be able to withstand in the evil day, and having done all, to stand.” (Ephesians 6:13)