This reading is Daniel 9.
The Israelites were captive in Babylon because they had repeatedly rejected the warnings that God had given them through various prophets. God had given his usual Old Testament message: Obey him and receive blessings or disobey and receive consequences. Daniel knew that God had promised to return the Israelites to Jerusalem after 70 years as Jeremiah had written:
Jeremiah 25:11-12 This whole country will become a desolate wasteland, and these nations will serve the king of Babylon seventy years. “But when the seventy years are fulfilled, I will punish the king of Babylon and his nation, the land of the Babylonians, for their guilt,” declares the Lord, “and will make it desolate forever.”
Daniel prayed wearing “sackcloth and ashes,” as those were signs of grief and/or repentance. Note that Daniel’s passionate prayer for mercy was answered as soon as he began to pray (v. 23). Feel the passion in v. 19: “O Lord, listen! O Lord, forgive! O Lord, hear and act! For your sake, O my God, do not delay, because your city and your people bear your Name.”
Regarding the prophecy of the seventy ‘sevens,’ it is typically understood that each item represented one year. Therefore, this would have been 490 years. Some believe that the first 69 ‘sevens’ represent the time from Daniel to Christ’s crucifixion and that the final ‘seven’ is part of the great tribulation that is still to come. Therefore, it would predict Jesus’ first and second coming.
The next reading is Daniel 10.