Only this is true prayer, which only a Christian can pray. In prayer Christians speak to their heavenly Father on the basis of the precious promises in his Word. All speaking with God takes place in Jesus' name, in the confidence that through Jesus alone God is our dear Father and we unworthy sinners are his dear children. True prayer is therefore an expression of Christian faith. When therefore Christians join in prayer they give expression to their common faith.
Joint prayer is an expression of fellowship in faith.
All of God's children, who are individually known to God alone, constantly pray with and for us. There is a blessed, invisible prayer fellowship that takes place at all times, in which the hearts of all believers are raised together to the throne of grace in supplication and thanksgiving. In this sense we are joined in common prayer with all those children of God, whom the Lord preserves for himself in erring church bodies, for example, in the church of the pope, who is the Antichrist. We stand before God not only as individual believers, but as believers who are closely united with all other believers here on earth and there in heaven as his dear family. But outward, visible prayer fellowship, of which we are now speaking, comes about in this way that we consciously select certain people in order to give joint expression of a common faith.