There are a few basic factors for the formation of ‘Arūz which are supportive in the understanding of basics of Arūz. This article is a   study of those factors and sources which proved helpful to Khalīl bin Aḥmad in the formation of metrical system. First, motivational sources of ‘Arūz; second, natural source of ‘Arūz; and third, standardized sources for extraction of ‘Arūz. These historic sources have been analyzed which Khalīl adopted as standard in the formation of ‘Arūz to form a code and made it applicable for poetry.