Exodus 26:2

“Moreover you shall make the tabernacle with ten curtains of fine twined linen, and blue, and purple, and scarlet, with cherubim. You shall make them with the work of a skillful workman.

Five curtains shall be coupled together to one another, and the other five curtains shall be coupled to one another.

You shall make loops of blue on the edge of the one curtain from the edge in the coupling, and you shall do likewise on the edge of the curtain that is outermost in the second coupling.

You shall make fifty loops in the one curtain, and you shall make fifty loops in the edge of the curtain that is in the second coupling. The loops shall be opposite one another.