"Now faith is the substance of things hoped for, the evidence of things not seen. For by it the elders obtained a good report. Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear." -- Hebrews 11:1-3
What is faith? Very simply stated, faith is taking God at his Word and acting upon God's revelation. On one occasion, when the disciples had fished all night and caught nothing, the Lord told them to cast their nets on the right side of the ship. Taking him at his word, they cast the nets one more time and took in more fish than their boat could hold (Luke 5:1-7; John 21:3-7). When they needed money to pay taxes, the Lord sent Peter out to catch a fish with the promise that he would find the money needed in the mouth of the first fish he caught (Matt. 17:24-27). Believing Christ, Peter went fishing! When the Lord told Peter to come to him upon the water, Peter believed that he could; and he did (Matt. 14:28-29).
Faith simply believes what God reveals both about himself and about all things in his creation and acts accordingly. Faith submits to God's revelation regarding himself, his Son, and his salvation, the creation of the world, the fall of man, and the providence of God, grace, the resurrection, and judgment. That is the nature of faith. It takes God at his Word.
THIS FAITH IS AN INDEX OF THE HEART. Faith is the proof of love. Love "believeth all things" (1 Cor. 13:7). If I truly love God, I believe him. If I do not believe him, I do not love him.
FAITH IS THE PROOF OF GRACE. The evidence and proof of God's grace is not good works, though good works are the fruit of grace and faith. The proof of grace is faith. I read my name in the book of God's election by faith in Christ. I know that I have been redeemed because I trust Christ. Faith is what Christ purchased for his redeemed ones. I know that I am born again because I believe. And faith is the gift of God's saving grace.
FAITH INSPIRES PRAYER. When God told David what he would assuredly do, because David believed him, he prayed for God to do what he promised (2 Sam. 7:27).
FAITH PLEASES GOD (Heb. 11:6). The Scriptures tell us that Enoch pleased God. How? He walked with God by faith. "But without faith it is impossible to please him." We do the works of God, the works God requires of men, when we trust the Lord Jesus Christ (John 6:29). The only thing God requires of us, and the only thing he will accept from us, is faith in Christ (1 John 3:23). And even this is the gift of God (Eph. 2:8).
FAITH GLORIFIES GOD. Faith says, "God is true." All who believe God see the glory of God (John 11:40). No one else can. And all who behold the glory of God in the face of Christ glorify him.