When Abd-er-Rahman I. seized upon the citadel of the Gothic Christian kings, he found the Cordovese split up into various sects, such as the Gnostics, Priscillianists, Donatists, and Luciferians. These cults were, however, united in their detestation of the new creed of the East, which the victors sought to impose upon them. It is quite clear from the records of the more impartial Spanish historians, that the Sultan was a man of tolerant mould and a respecter of justice. His ambition was to erect a temple, which would rival in magnificence those of Baghdad, Jerusalem, and Damascus, and approach in sanctity to the fane of Mecca itself.
The Christian church in Cordova stood upon the site of the former Roman religious edifice dedicated to Janus, and upon this situation Abd-er-Rahman desired to rear his great mosque. Autocrat though he was, the monarch strove to maintain the conditions upon which the inhabitants had surrendered. He might have broken faith, and annexed the Christian building and the ground upon which it stood. But he honourably offered to buy the church and the plot from the conquered people. The negotiations of purchase were placed in the hands of the Sultan’s favourite secretary, Umeya Ibn Yezid.
At first the Christians refused to sell their cherished basilica, which had been divided into a temple of the faith of Christ and a fane for the worship of Allah. Here, in separate portions of the building, the conquerors and the conquered murmured their prayers and repeated their praises to their deities. How the Cordovese were induced to relinquish the church cannot be explained by any historical evidence that we are able to obtain from the writings of Arabians and Spaniards. Some authors have suggested that the Christians of Cordova were disheartened by adversity and the assaults of Islam upon their creed, and that they yielded to the suasion and counsels of Umeya Ibn Yezid, and sold their tabernacle to the invaders. At any rate it is manifest that Abd-er-Rahman won in the end, and that he was able to forward his project without showing violence to the natives of Cordova.
No doubt the Christians preferred to worship in their own buildings rather than to share the basilica with the infidels, and this preference may have influenced their spiritual leaders in meeting the request of the sultan and his agent. Under the terms of transference, the Cordovese were permitted to reconstruct the edifice formerly dedicated to St. Faustus, St. Januarius, and St. Marcellus, three martyrs whom they deeply revered. Immediately upon the conveyance of the church and its site to Abd-er-Rahman, the work of erecting the gorgeous mosque was begun with much enthusiasm and at the expenditure of huge sums of money. The Khalif was rich. Besides the treasure wrested from the Goths during the wars, he extracted a tithe upon the produce of the land and on manufactures. A tax was also laid upon every Christian and Jew in Andalusia. Beyond this, the Moorish kings were greatly enriched by the acquisition of the valuable mines of Spain, the quarries of marble, and other sources of wealth. From these revenues Abd-er-Rahman and his successors, Hisham, Abd-er-Rahman II., the greatest of the dynasty and the third of the line--and lastly, the extravagant Al-manzor--lavished heavy sums upon the designing, construction, and costly adornment of the Mosque.