Heidelberg Catechism, Lord’s Day 46
[Heidelberg's teaching on the Lord's Prayer is not just excellent teaching on prayer; it is also an excellent model of biblical exposition. Why do we say "our Father"? To awaken a childlike reverence and trust. Why do we say "in heaven"? So we don't underestimate God. The beautiful double-whammy of the opening line of the Lord's Prayer--its intimacy and its majesty--is brought out powerfully by a mere two questions and answers. Look.]
Q120. Why did Christ command us
to call God “our Father”?
A120. To awaken in us
at the very beginning of our prayer
what should be basic to our prayer—
a childlike reverence and trust
that through Christ God has become our Father,
and that just as our parents do not refuse us
the things of this life,
even less will God our Father refuse to give us
what we ask in faith.
Q121. Why the words
“in heaven”?
A121. These words teach us
not to think of God’s heavenly majesty
as something earthly,
and to expect everything
needed for body and soul
from God’s almighty power.