Exodus 39:30-31

30 They made the rosette of the holy diadem of pure gold, and wrote on it an inscription, like the engraving of a signet, "Holy to the Lord."
31 They tied to it a blue cord, to fasten it on the turban above; as the Lord had commanded Moses.
New Revised Standard Version Bible, copyright 1989, Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.