What does the Bible say about holiness to the Lord?

In Exodus 28:36-38, we see the high priest Aaron wearing a plate of pure gold inscribed with the words 'holiness to the Lord.' This signifies that all activities and offerings brought before God must be set apart for His purpose and be seen as holy. It highlights that the priest bore the iniquity of holy things, meaning even our best spiritual acts are tainted by sin. But through the priest's intercession, we have access to God, as He sees the holiness of our great High Priest, Jesus Christ, instead of our flawed offerings.