“The sagacity of Leo I, his successful defense of the Catholic faith against heresy, as well as his political intervention with Attila the Hun and Generic the Vandal, raised the prestige of the Holy See to unprecedented heights and earned for him the title of ‘the Great’, a distinction accorded by posterity to only two other popes, St Gregory I and St Nicholas I…
Amongst the sermons of St Leo which have been preserved is one which he preached on the festival of St Peter and St Paul, not long after the retreat of Attila. He begins by contrasting the fervor of the Romans at the moment of their deliverance with their increasing forgetfulness, and reminds them of the ingratitude of the nine lepers. “Therefore, my beloved’ he goes on to say, ‘lest you incur the like reproach, return to the Saviour: remember the marvels He has wrought amongst you. Beware of attributing your deliverance to the stars, as some people impiously do, but refer it only to the boundless mercy of God who softened the furious hearts of the barbarians. Your past negligence must be atoned for by an expiation which exceeds the offense, Let us use the respite accorded by our kind Master to work at amending our lives, so that St Peter and all the saints who have succored us in countless afflictions may second the tender supplications which we address on your behalf to the God of mercy through our Lord Jesus Christ.’”