The Treatise on Rights by Imam Zain al Abidin (A.S) -10

Rights of Ritual Prayer

"The right of your ritual prayer (sala`t) is that you know that it is an arrival before Allah and that through it you are standing before Him. When you know that, then you will stand in the station of him who is lowly, vile, beseeching, trembling, hopeful, fearful, and abased, and you will magnify Him who is before you through stillness and dignity. You will approach the prayer with your heart and you will perform it according to its bounds and rights. There is no strength save in Allah." 

As for the prayer, it is the greatest of all the religious rites, and the most important of them in Islam. It is the sacrifice of those who have reverential fear, as it has been mentioned in the tradition, and is an arrival before Allah.
Its right against the Muslim is that he knows that he is standing before the Almighty King, the Creator of the heavens and the earth and Giver of life. He should turn all his feelings and sentiments toward Allah. 

He should stand before Him in the station of him who is lowly, vile, beseeching that which is with Allah, fearful of His punishment, hopeful for His forgiveness and good pleasure. 

He should perform the prayers with stillness, dignity, humble limbs, and good whispered prayers. He should not occupy his mind with any of the world's affairs. He should ask Allah to forgive him his sins and offenses, and to release his neck from the Fire.