Verses with the word silk in the Old Testament (3 verses):

Proverbs 31:22
She maketh herself coverings of tapestry; her clothing is silk and purple.

Ezekiel 16:10
I clothed thee also with broidered work, and shod thee with badgers' skin, and I girded thee about with fine linen, and I covered thee with silk.

Ezekiel 16:13
Thus wast thou decked with gold and silver; and thy raiment was of fine linen, and silk, and broidered work; thou didst eat fine flour, and honey, and oil: and thou wast exceeding beautiful, and thou didst prosper into a kingdom.