For John Calvin, prayer was like a priceless treasure that God has offered to His people.
Calvin’s first rule of prayer was to enter into it with a full awareness of the One to whom we are speaking. The key to prayer is a spirit of reverence and adoration: “Let the first rule of right prayer be, to have our heart and mind framed as becomes those who are entering into converse with God.”
Calvin wrote of how easy it is for our minds to wander in prayer. We become inattentive, as if we were speaking to someone with whom we are easily bored. This insults the glory of God: “Let us know, then, that none duly prepare themselves [sic] for prayer but those who are so impressed with the majesty of God that they engage in it free from all earthly cares and affections.”
Calvin’s second rule of prayer was that we ask only for those things that God permits. Prayer can be an exercise in blasphemy if we entreat His blessing for our sinful desires: “I lately observed, men in prayer give greater license to their unlawful desires than if they were telling jocular tales among their equals.”
Calvin’s third rule of prayer was that we must always pray with genuine feeling. Prayer is a matter of passion: “Many repeat prayers in a perfunctory manner from a set form, as if they were performing a task to God … They perform the duty from custom, because their minds are meanwhile cold, and they ponder not what they ask.”
A fourth rule of prayer from Calvin was that it be always accompanied by repentance: “God does not listen to the wicked; that their prayers, as well as their sacrifices, are an abomination to them. For it is right that those who seal up their hearts should find the ears of God closed against them.”
Calvin said a humble submission is required: “Of this submission, which casts down all haughtiness, we have numerous examples in the servants of God. The holier they are, the more humbly they prostrate themselves when they come into the presence of the Lord.”
If I can summarize Calvin’s teaching on prayer succinctly, I would say this: The chief rule of prayer is to remember who God is and to remember who you are. If we remember those two things, our prayers will always and ever be marked by adoration and confession.
Ligonier.org