Many were persecuted by their unbelieving brethren. In order to retain their position in the church, some consented to be silent in regard to their hope; but others felt that loyalty to God forbade them thus to hide the truths which He had committed to their trust. Not a few were cut off from the fellowship of the church for no other reason than expressing their belief in the coming of Christ. Very precious to those who bore this trial of their faith were the words of the prophet: “Your brethren that hated you, that cast you out for My name's sake, said, Let the Lord be glorified: but He shall appear to your joy, and they shall be ashamed.” Isaiah 66:5 . GC 372.3 Angels of God were watching with the deepest interest the result of the warning. When there was a general rejection of the message by the churches, angels turned away in sadness. But there were many who had not yet been tested in regard to the advent truth. Many were misled by husbands, wives, parents, or children, and were ma…
"Hear the word of the Lord, ye that tremble at his word; Your brethren that hated you, that cast you out for my name’s sake, said, Let the Lord be glorified: but he shall appear to your joy, and they shall be ashamed."
Ellen White directly references Isaiah 66:5 in this passage.
"God designed to prove His people. His hand covered a mistake in the reckoning of the prophetic periods. Adventists did not discover the error, nor was it discovered by the most learned of their opponents. The latter said: “Your reckoning of the prophetic periods is correct. Some great event is about to take place; but it is not what Mr. Miller predicts; it is the conversion of the world, and not the second advent of Christ.” (See Appendix .) GC 373.2"
"And thou shalt remember all the way which the Lord thy God led thee these forty years in the wilderness, to humble thee, and to prove thee, to know what was in thine heart, whether thou wouldest keep his commandments, or no."
Both passages deal with God testing His people through a specific experience. In Deuteronomy, it's the 40 years in the wilderness; in EGW, it's the disappointment of the failed prophecy. The underlying principle of God using trials to reveal the heart is present in both.