“…Abraham grew strong in his faith as he gave glory to God, being fully convinced that God was able to do what he had promised” (Romans 4:20-21).
While inspiring our faith, this passage also exposes a couple of issues at the heart of our doubts and struggles. The first is somewhat obvious: We are not convinced God is able to do what God has promised. But the second issue is subtler: We don’t know what it is God has promised. It’s hard to believe God—or anyone—keeps his promises when we don’t know what the promises are.
In Abraham’s case it was Sarah’s miraculous conception and the birth of Isaac, the “son of promise.” Abraham believed this promise of God through years of waiting and serious doubting, and despite the odds and circumstances. But much larger even than Isaac, God’s promise was the covenantal relationship. Abraham had to believe God’s promise to be God—to be his God and the God of those he loved, from generation to generation.
I don’t know how much or often God makes specific promises to us on the order of miraculous conceptions. Rarely, I suppose. He does promise in Jesus to care for us and to provide for our needs. And we see this in the natural world (why must it be considered any less miraculous?) as, every moment, babies are conceived and bread comes forth from the earth and water is transformed into the fruit of the vine. But the daily miracle of our existence in Christ is God’s promise to be “with you always.” And he seals that promise—through death, resurrection, and ascension—with the indwelling of the Holy Spirit. This is the angle from which we are to approach all those more specific promises we hope will come to pass.