VI. Zeal in rooting out heresy will make other pious duties more acceptable
Display then a holy zeal of religious vigilance, and let all the faithful rise in one body against these savage enemies of their souls. For the merciful God has delivered a certain portion of our noxious foes into our hands in order that by revelation of the danger the utmost caution might be aroused. Let not what has been done suffice, but let us persevere in searching them out: and by God's aid the result will be not only the continuance in safety of those who still stand, but also the recovery from error of many who have been deceived by the devil's seduction. And the prayers, and alms, and fasts that you offer to the merciful God shall be the holier for this very devotion, when this deed of faith also is added to all your other godly duties. On Wednesday and Friday, therefore, let us fast, and on Saturday let us keep vigil in the presence of the most blessed Apostle Peter; who, as we experience and know, watches unceasingly like a shepherd over the sheep entrusted to him by the Lord, and who will prevail in his entreaties that the Church of God, which was founded by his preaching, may be free from all error, through Christ our Lord. Amen.
Source: Sermons (New Advent)