Al-Farahidi's first work was in the study of Arabic prosody, a field for which he is credited as the founder.[43][44] Reportedly, he performed the Hajj pilgrimage to Mecca while a young man and prayed to God that he be inspired with knowledge no one else had.[3] When he returned to Basra shortly thereafter, he overheard the rhythmic beating of a blacksmith on an anvil and he immediately wrote down fifteen metres around the periphery of five circles, which were accepted as the basis of the field and still accepted as such in Arabic language prosody today.[4][5][6][7] Three of the meters were not known to Pre-Islamic Arabia, suggesting that al-Farahidi may have invented them himself.[45] He never mandated, however, that all Arab poets must necessarily follow his rules without question, and even he was said to have knowingly broken the rules at times.[46]