Heidelberg Q. 120. Why has Christ commanded us to address God as Our Father?
A. To awaken in us at the very beginning of our prayer that childlike reverence and trust toward God which should be basic to our prayer: God has become our Father through Christ and will much less deny us what we ask of Him in faith than our fathers would refuse us earthly things.

Heidelberg Q. 121. Why is there added, Who art in heaven?
A. These words teach us not to think of God's heavenly majesty in an earthly manner, and to expect from His almighty power all things we need for body and soul.