"From the pillar of cloud Christ declared concerning the Sabbath: “Verily My Sabbaths ye shall keep: for it is a sign between Me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you.” Exodus 31:13 . The Sabbath given to the world as the sign of God as the Creator is also the sign of Him as the Sanctifier. The power that created all things is the power that re-creates the soul in His own likeness. To those who keep holy the Sabbath day it is the sign of sanctification. True sanctification is harmony with God, oneness with Him in character. It is received through obedience to those principles that are the transcript of His character. And the Sabbath is the sign of obedience. He who from the heart obeys the fourth commandment will obey the whole law. He is sanctified through obedience. 6T 350.1"
"Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you."
Ellen White directly references Exodus 31:13 in this passage.