Tefilla. The basic idea of Prayer is a Mitzvah (one of the 613.) The idea of Davening quietly was introduced by Chana. The text of Prayer begins with the אנשי כנסת הגדולה (the members of the great assembly) who did it because language was becoming adulterated and people no longer spoke clearly and precisely. What did the אנשי כנסת הגדולה actually write? The basics: Pesukei DiZImra (Brachos) the blessings of Shma, the Amida, Bentching And… Brachos כל מטבע שטבעו חכמים בבברכות means the אנשי כנסת הגדולה.
Tefilla Min HaTorah and from the Anshei Kneses HaGedolah.
