“I believe in God.”
I have had some interesting conversations that began with that statement. Sadly, few who make it can honestly drop that little preposition: in. Most people I know will say, yes, I believe in God, but when confronted with what God has said about himself and about them, have to admit that, well, no, I don’t actually believe that. Then I have told them that it isn’t those who believe in God who will be saved, but only those who believe God. And this is the great stumbling block.
Here are a few words from Luther on what it means to believe God:
Abraham believed God (4:3). This must be understood in the sense that Abraham was always ready to believe God. He steadfastly believed God. This fact we learn from Genesis 12 and 13, where we are told that Abraham believed God who called and commanded him to leave his country and go into a strange land. Again he believed God when, according to Genesis 1:22ff., he was commanded to slay his son Isaac, and so forth. Whatever he did, he did by faith as the Apostle declares in Hebrews 11:8–10. So also what is stated in our text (v. 3) is said of Abraham’s faith in general, and not merely with regard to the one promise recorded in Genesis 15:4–6. To believe God means to trust him always and everywhere.
—Martin Luther, Luther’s Commentary on Romans, trans. J. Theodore Mueller (Grand Rapids, Zondervan, 1954), 66.