Exodus 38:7 in the King James Version
And he put the staves into the rings on the sides of the altar, to bear it withal; he made the altar hollow with boards.
Context
6 He made the poles of acacia wood, and overlaid them with bronze.
7 He put the poles into the rings on the sides of the altar, with which to carry it. He made it hollow with planks.
8 He made the basin of bronze, and its base of bronze, out of the mirrors of the ministering women who ministered at the door of the Tent of Meeting.