601. Prayer and Request
A prayer is what our sages have arranged for us. This is in general. A request is a personal matter, what each one asks, what he feels he needs.
Hence, a prayer should be with the mouth, or else there is no grip to the prayer, since there are words in the words of the prayer that a person has no idea why they are needed. Hence, the grip on the prayer is when a person says the words that are written.
Conversely, a request that a person asks, when he feels what he is lacking, he need not utter it verbally. Rather, it is enough that he feels in the heart what he is missing. In other words, what a person feels he needs is called “a request,” when the heart wants that someone who has the ability to give him what he wants will give to him.
Since a religious person wants the Creator to satisfy his wish, and the Creator knows the thought of each and every one, what his heart demands, it is therefore enough if a person feels his deficiency—this is a prayer to the Creator for the deficiencies in his heart. Conversely, the words of the prayer were established in the hearts of our sages, what they had in their hearts.