Imam al-Sadiq (AS) said, ‘Worshippers are of three types: people who worship Allah, Mighty and Exalted, out of fear, and that is the worship of a slave; people who worship Allah, Blessed and most High, seeking to be rewarded thereof, and that is the worship of an employee; and people who worship Allah, Mighty and Exalted, out of love for Him, and that is the worship of free men and is the best type of worship.