The Bee - 16:102
"Say, "The Holy Spirit has sent it down from your Lord with the truth, that it may strengthen those who believe and be a guidance and good news for the Muslims."
Fortified believer:
The Cave/18:14
"When they got up, We had made their hearts firm: "Our Lord is the Lord of the heavens and the earth. We shall have no gods besides Him. Otherwise, we would have spoken a false word."