"Windows Open Toward Jerusalem"
The key to this verse and indeed to the whole chapter, is that little parenthesis - "his windows were open in his chamber toward Jerusalem."
These chapters of Daniel are not in chronological order. Chapters 7 and 8 both come before chapter 5, and then after chapter 5 comes chapter 9 which occurred in the first year of Darius. Chapter 6, although it does not say so, clearly occurred after the first year of Darius: there was an order of things already in the realm, there was a relationship between Darius and Daniel, there were enmities which must have taken time to mature: so that chapter 6 follows chapter , and chapter 9 explains the open windows.
A Revelation of God's Purpose
Daniel had a revelation from God. Chapter 9 tells us how he humbled himself before God over the state of God's people and of God's city, and how from heaven there came illumination, and Daniel, with the eyes of the spirit, saw the Divine purpose in its immediate effect (for Jerusalem was to be rebuilt) and in its larger, fuller and final outworking - the day when the people of God and the city of God should indeed be a praise to Him, all transgression forever finished, everlasting righteousness brought in, all the prophecies fulfilled, and God's dwelling place with men. Daniel saw that; he was able to enter into God's purpose concerning His people; and, whether his windows had been open before that or not, from that day onward they were open - the windows that looked toward Jerusalem - and Daniel made it the persistent, continual, purposeful exercise of his heart to get down before those open windows and pray for God's purposes.
Daniel's Committal to God's Purpose
The opening of the windows was a symbolic act. It meant that he was committed to God and to that to which God was committed; he was with God for that which God intended to do; and the open windows were, humanly speaking, his undoing. Other people saw him at the open windows and realized that here was a trap, a way by which they could ensnare him. And that is, as I understand it, the setting for this chapter 6 - not a young man, but the old servant of the Lord, being faced with two alternatives, either to close his windows and leave off pursuing this utter attitude of cooperation with God, or else to go into the lions' den.
The Enemy's Antagonism
Of course, as far as the story goes, it was just the hatred of men and a convenient way of getting rid of him. But we know that there are spiritual lessons in it, and that it always happens like this - that heavenly revelation, and the committal of the heart utterly to the Lord for its fulfillment, provoke an assault which is meant either to make us desist or to destroy us.
Earlier on, Daniel's companions had been in a similar position with regard to the fiery furnace; but for them it was a matter of whether they were on the Lord's side or not. If they were on the Lord's side, well then, the fiery furnace; if they wanted to avoid the fiery furnace, they must break with the Lord. And we know, and Daniel knew, how the Lord delivered. We all know something of that as Christians. So soon as we are truly on the Lord's side we meet, as they met, an antagonism which calls upon us either to desist or to know the fiery furnace.
I think this experience of Daniel's marks a step in advance of that. This was not for him a question of whether he was the Lord's or not. He could have closed his windows, he could have desisted from this which was the cause of his being thrown into the lions' den, without breaking with the Lord; in the quietness of his own heart, in the seclusion of his own rooms, he could have prayed. It was not now the question of whether he was the Lord's or not, but the question of an utter position in the light of heavenly revelation, or of desisting from that. It is always so. That is the treatment that we may expect if we too have seen something of what God is desiring and intending to do, and have given Him our hearts and our hands that we are with Him for it.
(continued with # 7 - (The Delivering Power of the Heavenly Vision)