Shortly before the fall of Babylon, when Daniel was meditating on these prophecies [of Isaiah and Jeremiah] and seeking God for an understanding of the times, a series of visions was given him concerning the rise and fall of kingdoms. With the first vision, as recorded in the seventh chapter of the book of Daniel, an interpretation was given; yet not all was made clear to the prophet. “My cogitations much troubled me,” he wrote of his experience at the time, “and my countenance changed in me: but I kept the matter in my heart.” Daniel 7:28. TA 142.1
Through another vision further light was thrown upon the events of the future; and it was at the close of this vision that Daniel heard “one saint speaking, and another saint said unto that certain saint which spake, How long shall be the vision?” The answer that was given, “Unto two thousand and three hundred days; then shall the sanctuary be cleansed,” filled him with perplexity. Earnestly he sought for the meaning of the vision. He could not understand the relation sustained by the seventy years’ captivity, as foretold through Jeremiah, to the twenty-three hundred years that in vision he heard the heavenly visitant declare should elapse before the cleansing of God's sanctuary. The angel Gabriel gave him a partial interpretation; yet when the prophet heard the words, “The vision ... shall be for many days,” he fainted away.... TA 142.2
Still burdened in behalf of Israel, Daniel studied anew the prophecies of Jeremiah. They were very plain.... TA 143.1
With faith founded on the sure word of prophecy, Daniel pleaded with the Lord for the speedy fulfillment of these promises.—Prophets and Kings, 553, 554. TA 143.2
As Daniel's prayer is going forth, the angel Gabriel comes sweeping down from the heavenly courts, to tell him that his petitions are heard and answered. This mighty angel has been commissioned to give him skill and understanding—to open before him the mysteries of future ages. Thus, while earnestly seeking to know and understand the truth, Daniel was brought into communion with Heaven's delegated messenger.—The Review and Herald, February 8, 1881. TA 143.3
Even before he [Daniel] had finished pleading with God, Gabriel again appeared to him and called his attention to the vision he had seen prior to the fall of Babylon at the death of Belshazzar. The angel then outlined in detail the period of the seventy weeks.—The Review and Herald, March 21, 1907. TA 143.4