Faith and the Reason to Believe God

How would you sell a retirement fund? Would you persuade your client of its security by telling them the funds were already in it? If so, what motive could you give them that might compel them to invest their own? It seems to me that we often expect God to show us what the “pay off” will be in this or that situation before we will trust him in it; we expect to first see the money in the account before we put it there. Instead, the promise of the gospel is that the account is secure: in Jesus, God is now for us at all times and is never against us and will never disappoint those who believe such a promise – and if we are to enjoy the security and stability of such a God, we must believe that promise; we must “invest” our faith in him by believing such promises. And in doing so, we will discover the unfailing satisfaction and stability of God as our "desire" and "portion" (Ps. 73:25, 26). To expect to see God honor his promise without first believing him is not the exercise of faith but the denial of it.

Herman Bavinck puts it like this:

Christ secured [a] full, real, and total salvation. Faith, accordingly, is not a work, a condition, an intellectual assent to the statement “Christ died for you” but [the] act of [relying] on Christ himself, …. It is a living [i.e. “investing”] faith….

[H]umans are always inclined to reverse the God-ordained order [of faith and assurance]. They want to be sure of the outcome before using the means and in order to be exempt from using the means. But it is the will of God that we shall take the way of faith, and then he unfailingly assures us of complete salvation in Christ. (RD, IV, 37)

In wanting proof up front, it is as though we say to God, “You are not worth trusting in this or
that situation (let alone for eternity) till you show me what you intend to do today or tomorrow for me and I approve of it; till then, I will not trust you.” Faith that pleases God rests, like David,
in the goodness and mercy of God to be good and merciful toward us because of his Son, Jesus.