Martin M. van Brauman
Man’s obligation to pray can be found in Deuteronomy 11:14 in the commandment to serve God with all your heart. What is service with all your heart? At the pinnacle of the universe stands prayer.
. . . when the Holy Temple stood, “service” was the sacrificial service, and following its destruction, prayer took the place of the offerings . . . man’s obligation to pray is the commandment that man should serve God with all your heart (Deuteronomy 11:14). What is the service of the heart? . . . when the Torah speaks of “service,” it refers to the offerings brought in the Temple or on an altar . . . What service is performed in the heart? . . . That service . . . is prayer . . . It equates the . . . daily prayer to the sacrificial service in the Temple, the most sacred place on earth. 
The sincere prayer of every person represents their personal “service of the heart” that is elevated to the “pinnacle of the universe!” The Divine Presence of God lives not in a building, but in the human heart wherever its worshippers gather for They shall make a Sanctuary for Me – so that I may dwell among them – Exodus 25:8.
Since the destruction of the Jewish Temple in the 1st century, prayer not only takes the place and purpose of sacrifice, but is more important than sacrifice. The purpose of the sacrificial service was to bring about a person’s closeness and dedication to Godliness. Pray is the elevation of the soul unto God.
The basic function of prayer is not its practical consequences, but the metaphysical formation of a fellowship consisting of God and man. Prayer is not just a series of requests to God, but prayer is an engagement, even a confrontation, with God. God initiated dialogue with man at Mount Sinai with Moses and the Jewish peoplehood. Through His Word, God speaks to us and we speak to God through prayer and this dialogue is created by the linking of Bible study and prayer.
 Siddur, Wasserman Edition (1st ed., 1st Impression 2010), p. xxiii.
 Jonathan Sacks, Covenant & Conversation: Exodus: The Book of Redemption, (1st ed. 2010), p. 192.
 David Patterson, Wrestling With the Angel: Toward a Jewish Understanding of the Nazi Assault on the Name, (1st ed. 2006), p. 68.
 Chumash, Genesis 8:20, commentary.
 Patterson, p. 68.
 David Patterson, Overcoming Alienation: A Kabbalistic Reflection on the Five Levels of the Soul, (1st ed. 2008), p. 167.