In chapter three of the Book of Daniel, King Nebuchadnezzar II of Babylon builds a statue from gold, and he tells everyone to worship it. Some Jews living in Babylon named Azariah, Hananiah, and Mishael refuse to worship the statue. The king gets mad so he has them put into a big furnace to kill them. An angel protects them from the fire, and the king decides to let them go.
In the longer version of the story, Azariah's prayer is put after the three men are put into the furnace, starting at verse 24. In the prayer, Azariah says that he and the other people of Judah (part of ancient Israel) have sinned against God. He says that they are sorry and asks for God's protection.
The Song of the Three Holy Children is another part of the longer version of the Book of Daniel. It is sung by Azariah, Hananiah, and Daniel, who praise God and want everyone else to join them in prayer.