Pen Lid

A favourite illustration of mine to explain what it means that someone or something is "holy". The lid of the top pen is "holy" - that is set apart from the pen. The lid of the bottom pen is not "holy" - it is not set apart.
God is holy - like the pen lid that is set apart from the pen. By nature we are not holy. Jesus died to make us holy - to sanctify us - to set us apart as God's children.
To make something "holy" is to "sanctify" it, which is the same Greek word. It is also the same word in the Lord's prayer, translated "Hallowed" in "Hallowed be Your Name". The prayer therefore means, "Father, may Your Name (all You are) be set apart as holy." Now that is a prayer to pray.