2 In the first year of his reign, I, Daniel, was meditating on the Scriptures that gave, according to the Word of God to the prophet Jeremiah, the number of years that Jerusalem had to lie in ruins, namely, seventy. 3 I turned to the Master God, asking for an answer - praying earnestly, fasting from meals, wearing rough penitential burlap, and kneeling in the ashes.
Matthew Henry's Commentary on Daniel 9:2-3
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.