The thing referred to in verse 17 was a dream that the king had. He couldn't remember it, and he demanded that the wise men of Babylon remind him of what he dreamed, and also interpret it. The wise men, except Daniel, declared that no one could be expected to do that. But Daniel, and his friends, prayed for help, and got it. Then Daniel thanked God, as he should have, and we should, too.
This is part of a series on prayers in the Bible. The previous post is here. Thanks for reading.