From the Heidelberg Catechism for the Lord’s Day, November 10

116. Why is prayer necessary for Christians?

Because it is the chief part of thankfulness which God requires of us, and because God will give His grace and Holy Spirit only to those who earnestly and without ceasing ask them of Him, and render thanks unto Him for them.

117. What belongs to such prayer which is acceptable to God and which He will hear?

First, that with our whole heart we call only upon the one true God, who has revealed Himself to us in His Word,  for all that He has commanded us to ask of Him; second, that we thoroughly know our need and misery, so as to humble ourselves in the presence of His divine majesty; third, that we be firmly assured that notwithstanding our unworthiness He will, for the sake of Christ our Lord, certainly hear our prayer, as He has promised us in His Word.

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

All things necessary for soul and body, which Christ our Lord comprised in the prayer which He Himself taught us.

119. What is the Lord’s Prayer?

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 forgive our debtors. And lead us not into temptation, but deliver us from evil: for Thine is the kingdom, and the power, and the glory, forever. Amen