Ellen White to Brother Washburn, "Though sin had produced a gulf between man and his God, divine benevolence provided a plan to bridge that gulf.   And what material did He use?  A part of Himself, the brightness of the Father’s glory came to a world all seared and marred with the curse, and in his own divine character, in his own divine body, bridged the gulf, and opened a channel of communication between God and man."  Ellen White to Brother Washburn.  Letter 36a. 1890. 

“The Word was “in the beginning.” The mind of man cannot grasp the ages that are spanned in this phrase... We know that Christ “proceeded forth and came from God” (John 8:42), but it was so far back in the ages of eternity as to be far beyond the grasp of the mind of man.”  
E.J. Waggoner. 1890, Christ And His Righteousness. page 9.

R.A. Underwood wrote, “We are in ignorance of when this was done. We only know that it was in the eternity of the past; before the worlds and all that in them is, were created.”  
Review & Herald. Aug 6. Sept 17. 1889.

Uriah Smith wrote, “At the earliest epoch when a beginning could be, --a period so remote that to finite minds it is essentially eternity,-- appeared the Word.” “His beginning was not like that of any other being in the universe. It is set forth in the mysterious expressions, ‘his [God’s] only begotten Son’ (John 3:16; 1 John 4:9), ‘the only begotten of the Father’ (John 1:14), and ‘I proceeded forth and came from God.’ John 8:42.”
Looking Unto Jesus 1898. Uriah Smith.

Steven Haskell wrote, “Back in the ages, which finite mind cannot fathom, the Father and Son were alone in the universe. Christ was the first begotten of the Father, and to Him Jehovah made known the divine plan of Creation.”
The Seer of Patmos 1905.  Stephen Haskell. 

E.J. Waggoner said, “A son always rightfully takes the name of the father; and Christ, as “the only begotten Son of God,” has rightfully the same name. A son, also, is, to a greater or less degree, a reproduction of the father; he has, to some extent, the features and personal characteristics of his father;... and so Christ is the “express image” of the Father’s person. Heb. 1:3. As the Son of the self-existent God, He has by nature all the attributes of Deity.”  

A.T. Jones said, “In other words, Jesus Christ was born again. He came from heaven, God’s first-born, to the earth, and was born again.” “He whose goings forth have been from the days of eternity, the first-born of God, was born again, in order that we might be born again.”  
A.T. Jones RH Aug 1. 1899.

E.J. Waggoner wrote, "It is true that there are many sons of God, but Christ is the “only begotten Son of God,” and therefore the Son of God in a sense in which no other being ever was or ever can be." 
E. J. Waggoner. 1890. Christ And His Righteousness, pages 11.

Waggoner again, "As to when He (Christ) was begotten, it is not for us to inquire, nor could our minds grasp it if we were told. The prophet Micah tells us all that we can know about it in these words, “But thou, Bethlehem Ephratah, though thou be little among the thousands of Judah, yet out of thee shall He come forth unto Me that is to be ruler in Israel; whose goings forth have been from of old, from the days of eternity.” Micah 5:2, margin. There was a time when Christ proceeded forth and came from God, from the bosom of the Father (John 8:42; 1:18), but that time was so far back in the days of eternity that to finite comprehension it is practically without beginning."
 E. J. Waggoner. 1890. Christ And His Righteousness, pages 19-22.

C.W. Stone said of the birth of the Son in heaven.  “We may believe that Christ came into existence in a manner different from that in which other beings first appeared; that He sprang from the Father’s being in a way not necessary for us to understand.”   C. W. Stone. 1886. The Captain of Our Salvation, p. 17.

​J.M. Stephenson said, “To be the only begotten Son of God must be understood in a different sense than to be a Son by creation;  for in that sense all the creatures He has made are sons… He must therefore be understood as being the Son of God in a much higher sense than any other being.  His being the only begotten of the Father supposes that none except Him were thus begotten;  hence He is, in truth and verity the only begotten Son of God;  and as such He must be Divine; that is, be a partaker of the Divine nature.”   J M Stephenson. The Review and Herald, Nov. 14, 1854.

W.W. Prescott said, “As Christ was twice born, once in eternity, the only begotten of the Father, and again here in the flesh, thus uniting the divine with the human in that second birth…”  The Review and Herald, April 14, 1896.  This is before he became a Trinitarian.

Pioneers on the Son