Links to historically reviewed data would be suggested at this point.
Do some research on Egyptian religion and forms of prayer as affirmation. I really have no interest in spending the time needed to prove my statement on prayer. That said:
The invocation within a prayer unites our meditative state of consciousness with the power of the Word and our innate force of Will. The mechanism behind this is the same mechanism found in incantations. The word incantation comes from the Latin root "inner" and "sing". Originally someone qualified to perform the prayer/incantation was needed, average people of the community did not believe they possessed such a magical link as did their shaman, priest, or sorcerer.
The prayer works the same way that Haitian Vodou does, through the power of suggestion which can be explained more scientifically through neuroplasticity. With any incantation one is either seeking to create change within or to unveil some hidden truths also from within. The priest or shaman is the one who makes some change in objective reality by delivering the prayer or incantation. This is called an illocutionary force.
The concept of illocutionary acts was introduced into linguistics by the philosopher J. L. Austin in his investigation of the various aspects of speech acts. In Austin's framework, locution is what was said and meant, illocution is what was done, and perlocution is what happened as a result. When somebody says "Is there any salt?" at the dinner table, the illocutionary act is a request: "please give me some salt" even though the locutionary act (the literal sentence) was to ask a question about the presence of salt. The perlocutionary act (the actual effect), might be to cause somebody to pass the salt.