Prayer is the language of the spirit which communicates best with God. We pray for one another because God taught us the importance of interceding on behalf of one another. When the Samaritan woman conversed with the Lord, she argued about where one ought to worship. Since worship is the object of prayer, Christ corrected her thinking by informing her, saying, "God is Spirit, and those who worship Him, must worship in spirit and truth" (John 4:24). Thus, prayer is a necessary exercise of one's spirit which can only be directed toward God. People who never find contentment in their lives can attribute this failure to the void in their lives caused by not exercising their intrinsic need to pray, find God, and develop a real relationship with Him. St. Augustine's contemplation on the desire of happiness is settled by seeking God. "How then am I to seek You, Lord? when I seek you, my God, what I am seeking is a life of happiness. Let me seek you that my soul may live, for my body draws life from my soul, so does my soul draw its life from You."
Thus, it would be more selfish for us who know God and have a relationship with Him to keep this relationship solely to ourselves and not to share our prayers for others with Him that others may also come to know Him and have eternal life. It is Christ who taught us to pray for one another for this purpose, "I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me" (John 17:20,21).