Sanctification of the heart
The first instrument that God told Moses to build was the Ark of the Covenant. The length of it was two and a half cubit and a cubit and a half its width and height.
It was overlaid with pure gold which represents purity. The Lord told Moses to put the testimony with the Ten Commandments in the Ark. The Ark of the Covenant represents our hearts which must be purified with the word of God.
“And they shall make an Ark of acacia wood; two and a half cubits shall be its length, a cubit, and a half its width, and a cubit and a half its height. And you shall overlay it with pure gold, inside and out you shall overlay it, and shall make on it a molding of gold all around… (Exodus 25:10-16)