Heidelberg Catechism · 1563

Q116. Why is prayer necessary for Christians?

Because prayer is the most important part of the thankfulness which God requires of us. 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.
Answer · Heidelberg Catechism

Scripture proofs

  1. [1]
    Psalms 50:14-15

    Offer unto God thanksgiving; and pay thy vows unto the most High: And call upon me in the day of trouble: I will deliver thee, and thou shalt glorify me.

    Psalms 116:12-19

    What shall I render unto the Lord for all his benefits toward me? I will take the cup of salvation, and call upon the name of the Lord. I will pay my vows unto the Lord now in the presence of all his people. …

    1 Thessalonians 5:16-18

    Rejoice evermore. Pray without ceasing. In every thing give thanks: for this is the will of God in Christ Jesus concerning you.

  2. [2]
    Matthew 7:7-8

    Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you: For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened.

    Luke 11:9-13

    And I say unto you, Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you. For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened. If a son shall ask bread of any of you that is a father, will he give him a stone? or if he ask a fish, will he for a fish give him a serpent? …

Proof texts as given in the original; verse text from the King James Version.