Muslim philosophers who has attended to ethics based on a virtue-based approach believe that virtue is recognizable based on something in middle situated around which one or several vices are situated. According to the mentioned regulation, prayer is an ethical virtue which is considered as a subcategory of justice criterion. This includes a set of virtues that adorning with each virtue ends in purification from a vice which is opposed to it. An explanation of prayer as a virtue is given in this paper and the way of its opposing vices is analyzed.