"His adversaries watch him an entire day. Three times he has repaired to his chamber, and three times the voice of earnest intercession has been heard. The next morning the complaint is made to the king that Daniel, one of the captives of Judah, has set at defiance his decree. When the monarch heard these words, his eyes were at once opened to see the snare that had been set. He was sorely displeased with himself for having passed such a decree, and labored till the going down of the sun to devise a plan by which Daniel might be delivered. But the prophet's enemies had anticipated this, and they came before the king with these words: “Know, O king, that the law of the Medes and Persians is, That no decree nor statute which the king establisheth may be changed. SL 44.1"
"Now when Daniel knew that the writing was signed, he went into his house; and his windows being open in his chamber toward Jerusalem, he kneeled upon his knees three times a day, and prayed, and gave thanks before his God, as he did aforetime."
This is another clear and direct retelling of events from Daniel 6, specifically focusing on Daniel's continued prayer despite the decree. The confidence is very high.
"“Then the king commanded, and they brought Daniel, and cast him into the den of lions. Now the king spake and said unto Daniel, Thy God whom thou servest continually, he will deliver thee” ( verses 15, 16 ). A stone was laid upon the mouth of the den, and sealed with the royal seal. “Then the king went to his palace, and passed the night fasting: neither were instruments of musick brought before him: and his sleep went from him” ( verse 18 ). SL 44.2"
"Then the king commanded, and they brought Daniel, and cast him into the den of lions. Now the king spake and said unto Daniel, Thy God whom thou servest continually, he will deliver thee."
This is a direct quotation and paraphrase of Daniel 6:16 and 6:18. The connection is undeniable and the confidence is very high.
"Then the king went to his palace, and passed the night fasting: neither were instruments of musick brought before him: and his sleep went from him."
EGW directly quotes Daniel 6:18.