EGW and the "...the self-existent, eternal, unchangeable One..."
"These are wonderfully solemn and significant statements. It was the Source of all mercy and pardon, peace and grace, the self-existent, eternal, unchangeable One, who visited His exiled servant on the isle that is called Patmos." (EGW, SDA Bible Commentary, Vol. 7, page 955.)
"Is—was—is to come; a description of Christ as Jehovah, self-existent, unchangeable, and eternal....The source of grace, mercy, and peace, is the self-existent, eternal, unchangeable Jehovah; and for the manifestation of himself as the Father, the Son, and the Holy Ghost, in redeeming and sanctifying men, he is worthy of, and will receive the highest glory for ever." (The Family Bible: The New Testament, By Justin Edwards, 1851, p. 400)