"The very strongest incentives to faithfulness are set before us, the highest motives, the most glorious rewards. Christians are to be Christ's representatives, sons and daughters of God. They are His jewels, His peculiar treasures. Of all who will maintain their steadfastness He declares: “They shall walk with Me in white: for they are worthy.” Those who reach the portals of eternal bliss will not count that any sacrifice which they have made was too great. 5T 368.1"
"Thou hast a few names even in Sardis which have not defiled their garments; and they shall walk with me in white: for they are worthy."
The EGW passage directly quotes Revelation 3:4, making it a clear and explicit allusion.