"Those who have gained an experience in this work have a special duty to perform in teaching others. Educate, educate, educate young men and women to sell the books which the Lord by His Holy Spirit has stirred His servants to write. God desires us to be faithful in educating those who accept the truth, that they may believe to a purpose and work intelligently in the Lord's way. Let inexperienced persons be connected with experienced workers, that they may learn how to work. Let them seek God most earnestly. These may do a good work in canvassing if they will obey the words: “Take heed unto thyself, and unto the doctrine.” 1 Timothy 4:16 . Those who give evidence that they are truly converted, and who take up the canvassing work, will see that it is the best preparation for other lines of missionary labor. 6T 330.1"
"Take heed unto thyself, and unto the doctrine; continue in them: for in doing this thou shalt both save thyself, and them that hear thee."
Ellen White directly references 1 Timothy 4:16 in this passage.