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

2 Chronicles 26:14
And Uzziah prepared for them throughout all the host shields, and spears, and helmets, and habergeons, and bows, and slings to cast stones.

Jeremiah 46:4
Harness the horses; and get up, ye horsemen, and stand forth with your helmets; furbish the spears, and put on the brigandines.