We need to be anchored in Christ, rooted and grounded in the faith. Satan works through agents. He selects those who have not been drinking of the living waters, whose souls are athirst for something new and strange, and who are ever ready to drink at any fountain that may present itself. Voices will be heard, saying, “Lo, here is Christ,” or “Lo, there”; but we must believe them not. We have unmistakable evidence of the voice of the True Shepherd, and He is calling upon us to follow Him. He says, “I have kept My Father's commandments.” He leads His sheep in the path of humble obedience to the law of God, but He never encourages them in the transgression of that law. TR 63.2
“The voice of a stranger” is the voice of one who neither respects nor obeys God's holy, just, and good law. Many make great pretensions to holiness, and boast of the wonders they perform in healing the sick, when they do not regard this great standard of righteousness. But through whose power are these cures wrought? Are the eyes of either party opened to their transgressions of the law? and do they take their stand as humble, obedient children, ready to obey all of God's requirements? ... TR 63.3
None need be deceived. The law of God is as sacred as His throne, and by it every man who cometh into the world is to be judged. There is no other standard by which to test character. “If they speak not according to this word, it is because there is no light in them.” Now shall the case be decided according to the Word of God, or shall man's pretensions be credited? Christ says, “By their fruits ye shall know them.”—Selected Messages 2:50. TR 63.4