Our Father Heidelberg Catechism
Question 120. Why has Christ commanded us to address God thus: Our Father?
To awaken in us, at the very beginning of our prayer, that filial reverence and trust toward God, which are to be the ground of our prayer; namely, that God has become our Father through Christ, and will much less deny us what we ask of Him in faith, than our parents refuse us earthly things.
Gal. 4:6. Because ye are sons, God hath sent forth the Spirit of His Son into your hearts, crying, Abba, Father.
Matt. 7:9–11. What man is there of you, whom if his son ask bread, will he give him a stone? Or if he ask a fish, will he give him a serpent? If ye then, being evil, know how to give good gifts unto your children, how much more shall your Father which is in heaven give good things to them that ask Him?
1 Pet. 1:17. Isa. 63:16. Eph. 3:14, 15.
Question 121. Why is it added: Who art in Heaven?
That we may have no earthly thought of the heavenly majesty of God; and may expect from His almighty power all things necessary for body and soul.
Acts 17:24, 25. God that made the world and all things therein, seeing that He is Lord of heaven and earth, dwelleth not in temples made with hands; neither is worshiped with men’s hands, as though He needed anything, seeing He giveth to all life, and breath, and all things.
Rom. 10:12. The same Lord over all is rich unto all that call upon Him.
 Heidelberg Catechism, Heidelberg Catechism, Revised Edition. (Cleveland, OH: Central Publishing House, 1907), 126–127.