Exodus 40:20
And he took and put the testimony into the ark, and set the staves on the ark, and put the mercy seat above upon the ark: And he took and put the testimony into the ark, and set the staves on the ark, and put the mercy seat above upon the ark:
The placing of the testimony inside the ark, the fitting of the staves to the ark, and the setting of the mercy seat above upon the ark was one deliberate step in the ordered arrangement of the tabernacle. Every detail of that arrangement was designed to impress Israel with the majesty and holiness of God and with the purity He requires in those who serve Him. That same order was also meant to represent God's character before the surrounding nations and to show what He desires His people to become.