In the Old Testament, the high priest’s crown had the significant inscription “Holiness to the Lord” written on it. This was placed prominently on the high priest’s forehead, in view of women and men worshipping in the temple.
“Holiness to the Lord” is conspicuously placed on the exterior of our temples, usually written on a plaque, engraved on a wall or keystone, or established elsewhere, almost always on the temple’s east side. President Russell M. Nelson states that the phrase “designates both the temple and its purposes as holy. Those who enter the temple are also to bear the attribute of holiness.”159
Joseph Smith spoke of the blessed time of the Millennium that “even upon the bells of the horses shall be written Holiness to the Lord,”160 meaning, even seemingly non-sacred things will be like unto the temple of the Lord during the Millennium.