Exod. 25:10   They shall make an ark of acacia wood; it shall be two and a half cubits long, a cubit and a half wide, and a cubit and a half high. 

Exod. 37:1   Bezalel made the ark of acacia wood; it was two and a half cubits long, a cubit and a half wide, and a cubit and a half high. 

Exod. 37:6   He made a mercy seat of pure gold; two cubits and a half was its length, and a cubit and a half its width.
 
Exod. 25:17   Then you shall make a mercy seat of pure gold; two cubits and a half shall be its length, and a cubit and a half its width. 

Exod. 25:18   You shall make two cherubim of gold; you shall make them of hammered work, at the two ends of the mercy seat. 

Exod. 40:20   He took the covenant and put it into the ark, and put the poles on the ark, and set the mercy seat above the ark.