"Christ is the source of our strength. He is the Vine, we are the branches. We must receive nourishment from the living Vine. Deprived of the strength and nourishment of that Vine, we are as members of the body without a head and are in the very position which Satan wishes us to be in, that he may control us as pleases himself. He works “with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. And for this cause God shall send them strong delusion, that they should believe a lie.” Spiritualism is a lie. It is founded upon the great original lie, “Ye shall not surely die.” Thousands cut off the Head, and the result is the members act without Jesus for their head, and another guides the body. Satan controls them. 1T 301.1"
"I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing."
EGW directly references the vine and branches imagery from John 15:5, making it an explicit allusion.
"And with all deceivableness of unrighteousness in them that perish; because they received not the love of the truth, that they might be saved. And for this cause God shall send them strong delusion, that they should believe a lie:"
EGW directly quotes 2 Thessalonians 2:10-11, making it an explicit allusion.
"But speaking the truth in love, may grow up into him in all things, which is the head, even Christ: From whom the whole body fitly joined together and compacted by that which every joint supplieth, according to the effectual working in the measure of every part, maketh increase of the body unto the edifying of itself in love."
Both passages discuss Christ as the head of the body (the church) and the importance of being connected to Him. While not a direct quote, the theme is clearly present.