"Anciently, when a king journeyed through the less frequented parts of his dominion, a company of men was sent ahead of the royal chariot to level the steep places and to fill up the hollows, that the king might travel in safety and without hindrance. This custom is employed by the prophet to illustrate the work of the gospel. “Every valley shall be exalted, and every mountain and hill shall be made low.” When the Spirit of God, with its marvelous awakening power, touches the soul, it abases human pride. Worldly pleasure and position and power are seen to be worthless. “Imaginations, and every high thing that exalteth itself against the knowledge of God” are cast down; every thought is brought into captivity “to the obedience of Christ.” 2 Corinthians 10:5 . Then humility and self-sacrificing love, so little valued among men, are exalted as alone of worth. This is the work of the gospel, of which John's message was a part. DA 135.1"
"Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ;"
Ellen White directly references 2 Corinthians 10:5 in this passage.
"Every valley shall be exalted, and every mountain and hill shall be made low: and the crooked shall be made straight, and the rough places plain:"
EGW uses Isaiah 40:4 as a springboard to discuss the spiritual leveling that occurs through the gospel, drawing a parallel between the physical preparation for a king's journey and the spiritual preparation for Christ's coming. While it quotes the verse, the primary connection is thematic.
"The rabbis continued their questioning: “Why baptizest thou then, if thou be not that Christ, nor Elias, neither that prophet?” The words “that prophet” had reference to Moses. The Jews had been inclined to the belief that Moses would be raised from the dead, and taken to heaven. They did not know that he had already been raised. When the Baptist began his ministry, many thought that he might be the prophet Moses risen from the dead, for he seemed to have a thorough knowledge of the prophecies and of the history of Israel. DA 135.2"
"And they asked him, and said unto him, Why baptizest thou then, if thou be not that Christ, nor Elias, neither that prophet?"
EGW explains the context of the question posed in John 1:25, elaborating on the Jewish expectations surrounding 'that prophet,' connecting it to Moses. This is more than a simple allusion; it's an explanation of the underlying beliefs that inform the verse.
"It was believed also that before the Messiah's advent, Elijah would personally appear. This expectation John met in his denial; but his words had a deeper meaning. Jesus afterward said, referring to John, “If ye are willing to receive it, this is Elijah, which is to come.” Matthew 11:14 , R. V. John came in the spirit and power of Elijah, to do such a work as Elijah did. If the Jews had received him, it would have been accomplished for them. But they did not receive his message. To them he was not Elijah. He could not fulfill for them the mission he came to accomplish. DA 135.3"
"And if ye will receive it, this is Elias, which was for to come."
EGW directly quotes Matthew 11:14 and interprets its meaning in relation to John the Baptist and Elijah.