Verses with the word millstones in the Old Testament (2 verses):

Isaiah 47:2
Take the millstones, and grind meal: uncover thy locks, make bare the leg, uncover the thigh, pass over the rivers.

Jeremiah 25:10
Moreover I will take from them the voice of mirth, and the voice of gladness, the voice of the bridegroom, and the voice of the bride, the sound of the millstones, and the light of the candle.