"The appointed time came to appear before the emperor. Charles V, seated upon his throne, surrounded by the electors and the princes, gave audience to the Protestant Reformers. The confession of their faith was read. In that august assembly the truths of the gospel were clearly set forth, and the errors of the papal church were pointed out. Well has that day been pronounced “the greatest day of the Reformation, and one of the most glorious in the history of Christianity and of mankind.”— Ibid., b. 14, ch. 7. GC 207.1"
"But the Lord said unto him, Go thy way: for he is a chosen vessel unto me, to bear my name before the Gentiles, and kings, and the children of Israel:"
Both passages describe individuals bearing witness to their faith before powerful rulers. Acts 9:15 speaks of Paul being chosen to bear God's name before kings, while the EGW passage describes the Reformers presenting their confession before Emperor Charles V. The connection lies in the parallel of presenting one's faith before authority.
"But a few years had passed since the monk of Wittenberg stood alone at Worms before the national council. Now in his stead were the noblest and most powerful princes of the empire. Luther had been forbidden to appear at Augsburg, but he had been present by his words and prayers. “I am overjoyed,” he wrote, “that I have lived until this hour, in which Christ has been publicly exalted by such illustrious confessors, and in so glorious an assembly.”— Ibid., b. 14, ch. 7. Thus was fulfilled what the Scripture says: “I will speak of Thy testimonies ... before kings.” Psalm 119:46 . GC 207.2"
"I will speak of thy testimonies also before kings, and will not be ashamed."
Ellen White directly references Psalms 119:46 in this passage.