Answer
Scripture will talk about God as mysterious, and I think part of that is that God is holy, and humans now, in our existence now after the Fall, are not. And so, there is a mystery of holiness and purity that is beyond our experiences as we exist now, and so there is a mystery there. I think also there's a mystery in terms of God's mercy. God doesn't act as humans do. He's not out for, as Shakespeare says, "a pound of flesh." He doesn't have our selfish instincts. And that can come off as mysterious. Then I would say also there's another way that at least the apostle Paul uses the word mysterious. Paul will talk about God's salvation plan as a mystery now revealed. In Ephesians 3, for example, he will talk about this mystery that has been made known now, this mystery that Gentiles are included with Jews in Christ to make the church. And Paul says this is mysterious and that the powers and principalities look on this in surprise at God's amazing wisdom, God's amazing love. So, those are some of the ways that Scripture talks about God as mysterious.