"John was a teacher of holiness, and in his letters to the church he laid down unerring rules for the conduct of Christians. “Every man that hath this hope in him,” he wrote, “purifieth himself, even as He is pure.” “He that saith he abideth in Him ought himself also so to walk, even as He walked.” 1 John 3:3 ; 2:6 . He taught that the Christian must be pure in heart and life. Never should he be satisfied with an empty profession. As God is holy in His sphere, so fallen man, through faith in Christ, is to be holy in his sphere. AA 559.2"
"And every man that hath this hope in him purifieth himself, even as he is pure."
Ellen White directly references 1 John 3:3 in this passage.
"eternity, that they might be holy. He gave His Son to die for them, that they might be sanctified through obedience to the truth, divested of all the littleness of self. From them He requires a personal work, a personal surrender. God can be honored by those who profess to believe in Him, only as they are conformed to His image and controlled by His Spirit. Then, as witnesses for the Saviour, they may make known what divine grace has done for them. AA 559.3"
"But as he which hath called you is holy, so be ye holy in all manner of conversation;"
Both passages emphasize the call to holiness. The EGW passage speaks of being holy and sanctified, while 1 Peter 1:15 directly commands believers to be holy. The connection is a strong thematic parallel.
"For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren."
Both passages discuss being conformed to the image of Christ. The EGW passage speaks of being conformed to God's image, while Romans 8:29 speaks of being predestined to be conformed to the image of His Son. The connection is a clear thematic parallel.