They could see his face, but they also saw God. Now from where did this powerful conviction come? Brethren, that kind of conviction does not arise on command, at the spur of the moment. That kind of conviction was the fruit of the demonstration of God in the lives of these three young men previous to this time and when their lives were on the line. They grew in faith over a period of time.
God is the God who is always the same. I Corinthians 10:13 applied to them just as it applies to you and me. He knew what they were able to endure. And they knew that He would provide a way of escape. So they said, Even if He does not choose to do that, we still are not going to bow down to your image.
Brethren, why do not more mighty deliverances occur to us? I think it is because we spend so little time fellowshipping with God that we do not see Him as an immediate and vitally important part of our lives. As a result of that, we are overwhelmed by the physical, by the around and the about.