"Saddened by Poisonous Errors John lived to see the gospel of Christ preached far and near, and thousands eagerly accepting its teachings. But he was filled with sadness as he perceived poisonous errors creeping into the church. Some who accepted Christ claimed that His love released them from obedience to the law of God. On the other hand, many taught that the letter of the law should be kept, also all the Jewish customs and ceremonies, and that this was sufficient for salvation, without the blood of Christ. They held that Christ was a good man, like the apostles, but denied His divinity. John saw the dangers to which the church would be exposed, should they receive these ideas, and he met them with promptness and decision. He wrote to a most honorable helper in the gospel, a lady of good repute and extensive influence: SL 63"
"Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace."
Both passages address the issue of legalism versus grace. EGW describes errors creeping into the church, including the idea that obedience to the law is sufficient for salvation without Christ's blood. This parallels Galatians 5:4, which states that those who seek justification by the law have fallen from grace.
"riveting upon their souls fetters which would never be broken. The prejudice and hatred against Christ which they obstinately cherished, was bringing ruin upon them as a nation and destroying their hopes of everlasting life. But John continued to present Christ to them as the only way of salvation. The evidence that Jesus of Nazareth was the Messiah was so clear that John declares no man needs to walk in the darkness of error while such light is proffered him. SL 63.1"
"Then spake Jesus again unto them, saying, I am the light of the world: he that followeth me shall not walk in darkness, but shall have the light of life."
EGW's statement about John presenting Christ as the only way of salvation and the evidence being so clear that no one needs to walk in darkness directly echoes the sentiment in John 8:12, where Jesus declares Himself as the light of the world, and those who follow Him will not walk in darkness.