Exodus 39:9

39:9 It was square – they made the breastpiece doubled, nine inches long and nine inches wide when doubled.

Exodus 28:16

28:16 It is to be square when doubled, nine inches long and nine inches wide.

Exodus 26:9

26:9 You are to join five curtains by themselves and six curtains by themselves. You are to double over the sixth curtain at the front of the tent.