"We feel sad to see professed Christians led astray by the false and bewitching theory that they are perfect, because it is so difficult to undeceive them and lead them into the right path. They have sought to make the exterior fair and pleasing, while the inward adorning, the meekness and lowliness of Christ, is wanting. The testing time will come to all, when the hopes of many who have for years thought themselves secure, will be seen to be without foundation. When in new positions, under varied circumstances, some who have seemed to be pillars in the house of God reveal only rotten timber beneath the paint and varnish. But the humble in heart, who have daily felt the importance of riveting their souls to the eternal Rock, will stand unmoved amid the tempests of trial, because they trusted not to themselves. “The foundation of God standeth sure, having this seal, The Lord knoweth them that are his” ( 2 Timothy 2:19 ). SL 12.1"
"Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his. And, Let every one that nameth the name of Christ depart from iniquity."
Ellen White directly references 2 Timothy 2:19 in this passage.