91 In the first year of Darius the son of Ahasuerus , of Median descent , who was made king over the kingdom of the Chaldeans - 2 in the first year of his reign , I, Daniel , observed in the books the number of the years which was revealed as the word of the Lord to Jeremiah the prophet for the completion of the desolations of Jerusalem , namely, seventy years .
Matthew Henry's Commentary on Daniel 9:1-2
Commentary on Daniel 9:1-3
(Read Daniel 9:1-3)
Daniel learned from the books of the prophets, especially from Jeremiah, that the desolation of Jerusalem would continue seventy years, which were drawing to a close. God's promises are to encourage our prayers, not to make them needless; and when we see the performance of them approaching, we should more earnestly plead them with God.