2 in the first year of his reign I, Daniel, understood by the books the number of the years specified by the word of the Lord through Jeremiah the prophet, that He would accomplish seventy years in the desolations of Jerusalem.
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.
Matthew Henry's Commentary on Daniel 9:2
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.