The Heidelberg Catechism: Lord's Day 51 

Question 126: What does the fifth request mean?

 Answer: Forgive us our debts, as we also have forgiven our debtors means, 
Because of Christ’s blood, do not hold against us, poor sinners that we are, any of the sins we do or the evil that constantly clings to us. [1]

 Forgive us just as we are fully determined, as evidence of your grace in us, to forgive our neighbors. [2]

[1] Ps. 51:1-7; 143:2; Rom. 8:1; 1 John 2:1-2; [2] Matt. 6:14-15; 18:21-35

The Heidelberg Catechism: Lord's Day 50 

125. Question: What is the fourth petition?

Answer: Give us this day our daily bread. That is: Provide us with all our bodily needs[1] so that we may acknowledge that Thou art the only fountain of all good,[2] and that our care and labor, and also Thy gifts, cannot do us any good without Thy blessing.[3] Grant therefore that we may withdraw our trust from all creatures, and place it only in Thee.[4]

[1] Ps. 104:27-30; 145:15, 16; Matt. 6:25-34. [2] Acts 14:17; 17:25; James 1:17. [3] Deut. 8:3; Ps. 37:16; 127:1, 2; I Cor. 15:58. [4] Ps. 55:22; 62; 146; Jer. 17:5-8; Heb. 13:5, 6.

The Heidelberg Catechism: Lord's Day 49 

124. Question: What is the third petition?

Answer: Thy will be done, on earth as it is in heaven. That is: Grant that we and all men may deny our own will, and without any murmuring obey Thy will, for it alone is good.[1] Grant also that everyone may carry out the duties of his office and calling[2] as willingly and faithfully as the angels in heaven.[3]

[1] Matt. 7:21; 16:24-26; Luke 22:42; Rom. 12:1, 2; Tit. 2:11, 12. [2] I Cor. 7:17-24; Eph. 6:5-9. [3] Ps. 103:20, 21.

The Heidelberg Catechism: Lord's Day 48 

123. Question: What is the second petition?

Answer: Thy kingdom come. That is: So rule us by Thy Word and Spirit that more and more we submit to Thee.[1] Preserve and increase Thy church.[2] Destroy the works of the devil, every power that raises itself against Thee, and every conspiracy against Thy holy Word.[3] Do all this until the fullness of Thy kingdom comes, wherein Thou shalt be all in all.[4]

[1] Ps. 119:5, 105; 143:10; Matt. 6:33. [2] Ps. 51:18; 122:6-9; Matt. 16:18; Acts 2:42-47. [3] Rom. 16:20; I John 3:8. [4] Rom. 8:22, 23; I Cor. 15:28; Rev. 22: 17, 20.

The Heidelberg Catechism: Lord's Day 47 

122. Question: What is the first petition?

 Answer: Hallowed be Thy Name. That is: Grant us first of all that we may rightly know Thee,[1] and sanctify, glorify, and praise Thee in all Thy works, in which shine forth Thy almighty power, wisdom, goodness, righteousness, mercy, and truth.[2] Grant us also that we may so direct our whole life– our thoughts, words, and actions– that Thy Name is not blasphemed because of us but always honored and praised.[3]

 [1] Jer. 9:23, 24; 31: 33, 34; Matt. 16:17; John 17:3. [2] Ex. 34:5-8; Ps. 145; Jer. 32:16-20; Luke 1:46-55, 68-75; Rom. 11: 33-36. [3] Ps. 115:1; Matt. 5:16.

The Heidelberg Catechism: Lord's Day 46

120. Question: Why has Christ commanded us to address God as Our Father?

Answer: 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.[1]

[1] Matt. 7:9-11; Luke 11:11-13.

121. Question: Why the words "in heaven"?

Answer: These words teach us not to think of God's heavenly majesty as something earthly, [1] and to expect everything for body and soul from his almighty power.[2]

[1] Jer. 23:23-24; Acts 17:24-25 [2] Matt. 6:25-34; Rom. 8:31-32

The Heidelberg Catechism: Lord's Day 45 

116. Question: Why is prayer necessary for Christians?

Answer: Because prayer is the most important part of the thankfulness which God requires of us.[1] Moreover, God will give His grace and the Holy Spirit only to those who constantly and with heartfelt longing ask Him for these gifts and thank Him for them.[2]

[1] Ps. 50:14, 15; 116:12-19; I Thess. 5:16-18. [2] Matt. 7:7, 8; Luke 11:9-13.

117. Question: What belongs to a prayer which pleases God and is heard by Him?

Answer: First, we must from the heart call upon the one true God only, who has revealed Himself in His Word, for all that He has commanded us to pray.[1] Second, we must thoroughly know our need and misery, so that we may humble ourselves before God.[2] Third, we must rest on this firm foundation that, although we do not deserve it, God will certainly hear our prayer for the sake of Christ our Lord, as He has promised us in His
Word.[3]

[1] Ps. 145:18-20; John 4:22-24; Rom. 8:26, 27; James 1:5; I John 5:14, 15; Rev. 19:10. [2] II Chron. 7:14; 20:12; Ps. 2:11; 34:18; 62:8; Is. 66:2; Rev. 4. [3] Dan. 9:17-19; Matt. 7:8; John 14:13, 14; 16:23; Rom. 10:13; James 1:6.

118. Question: What has God commanded us to ask of Him?

Answer: All the things we need for body and soul,[1] as included in the prayer which Christ our Lord Himself taught us.

[1] Matt. 6:33; James 1:17.

119. Question: What is the Lord's prayer?

Answer: Our Father who art in heaven, Hallowed be Thy Name. Thy kingdom come, Thy will be done, On earth as it is in heaven. Give us this day our daily bread; And forgive us our debts, As we also have forgiven our debtors; And lead us not into temptation, But deliver us from the evil one. For Thine is the kingdom, and the power, and the glory, for ever. Amen.[1]

[1] Matt. 6:9-13; Luke 11:2-4.