Daniel 9:11-15
Daniel 9:11
Yea, all Israel have transgressed thy law, even by departing, that they might not obey thy voice; therefore the curse is poured upon us, and the oath that is written in the law of Moses the servant of God, because we have sinned against him.
Daniel now confesses that all Israel has transgressed the law of God by departing from it and them seeking out the false gods and religions of surrounding nations.  When one walks away from God that also means they will be unable to hear the law of God.  If Christians neglect the study and reading of the Scriptures, then they deprive themselves of the voice of God who wrote the Scriptures.  The curse is the curse of the law which punishes transgressors of that law and the oath which God spoke to Israel has now come to pass.  The oath is found in Leviticus 26:14-35 and Deuteronomy 28:15-68.  They were now experiencing the consequences of their actions and sins against God.
Daniel 9:12
And he hath confirmed his words, which he spake against us, and against our judges that judged us, by bringing upon us a great evil: for under the whole heaven hath not been done as hath been done upon Jerusalem.
Daniel now states in his prayer that God confirmed the words that He spoke against Jerusalem if they disobeyed Him.  These can be found in Ezekiel 8-11.  God even spoke against the judges of Israel and that includes all the leaders that had gone corrupt. 
Jeremiah 11:9 (KJV)   And the LORD said unto me, A conspiracy is found among the men of Judah, and among the inhabitants of Jerusalem.
Ezekiel 22:25-27 (KJV)   There is a conspiracy of her prophets in the midst thereof, like a roaring lion ravening the prey; they have devoured souls; they have taken the treasure and precious things; they have made her many widows in the midst thereof.  {26} Her priests have violated my law, and have profaned mine holy things: they have put no difference between the holy and profane, neither have they shewed difference between the unclean and the clean, and have hid their eyes from my sabbaths, and I am profaned among them.  {27} Her princes in the midst thereof are like wolves ravening the prey, to shed blood, and to destroy souls, to get dishonest gain.
God had brought a great calamity upon Jerusalem and that was the removal of His people to pagan lands and the destruction of the city where God stated He would place His name for eternity only if they were obedient which did not happen and as a result lost their rights to the land.  Jerusalem was broken down but there had to come a regathering of the people because the Scriptures teach that Jesus had to be born in Bethlehem and He came through the line of Judah.
Daniel 9:13
As it is written in the law of Moses, all this evil is come upon us: yet made we not our prayer before the LORD our God, that we might turn from our iniquities, and understand thy truth.
Even in the midst of all the troubles they were facing, there was still no repentance nor seeking of the Lord to make amends for what they did and to turn to obedience.  Instead they continued in their iniquities until they were finally taken away to Babylon.  If they would have repented and turned back to the Lord, they would have come to know that God was faithful in keeping His promises and that He was faithful in bringing to pass the punishments that He listed in the law of Moses.  To turn away from their wicked ways would have brought them back into the truth and then deportation would not have happened.  When they were obedient, God’s hand of protection was upon them and that was a well-known fact of their history.
Daniel 9:14
Therefore hath the LORD watched upon the evil, and brought it upon us: for the LORD our God is righteous in all his works which he doeth: for we obeyed not his voice.

They adopted the idea that God was silent as one that sleeps.  Psalm 121:4 (KJV)   Behold, he that keepeth Israel shall neither slumber nor sleep.  Ezekiel 8:12 (KJV)   Then said he unto me, Son of man, hast thou seen what the ancients of the house of Israel do in the dark, every man in the chambers of his imagery? for they say, The LORD seeth us not; the LORD hath forsaken the earth.   The word “watched” carries with it the meaning of “remain awake or be alert.”  The Lord was well aware of their evil deeds and He brought the same evil deeds upon them.  They wanted to serve other gods, well now they were in a place which served false gods.  Daniel also states that God was totally righteous in bringing this calamity upon Judah because they were totally disobedient to God and walked away from His statutes.  The written word of God is as authoritative as the spoken word of God by the prophets or by an angel or by God Himself.
Daniel 9:15
And now, O Lord our God, that hast brought thy people forth out of the land of Egypt with a mighty hand, and hast gotten thee renown, as at this day; we have sinned, we have done wickedly.
Daniel now acknowledges the fact that God brought the nation of Israel out of bondage from the land of Egypt.  Apparently, these historical events have escaped the minds of the leaders and they forget these things while also forgetting how God judged Egypt and made it a lesser power never to be a world ruling nation again.  When God brought them out of Egypt, all the surrounding nations knew of Israel’s God because that event had given God renown among all the nations.  The word “renown” in the Hebrew carries with it the meaning of “standing, reputation, or fame.”  Now the surrounding nations have once again seen the hand of God in bringing His people into bondage for their disobedience to His law.  Daniel does not sugarcoat the reason why they are in Babylon, simply because they have sinned and done wickedness in the sight of God.