St. Pope Pelagius II

“For you know how the Lord in the Gospel declares: ‘Simon, Simon, behold Satan has desired you that he might sift you as wheat, but I have prayed to the Father for thee, that thy faith fail not, and thou, being converted, confirm thy brethren.’ See, beloved, the truth cannot be falsified, nor can the faith of Peter ever be shaken or changed.”


“For although the devil desired to sift all the disciples, the Lord testifies that He Himself asked for PEter alone and wished the others to be confirmed by him; and to him also, in consideration of a greater love which he showed the Lord before the rest, was committed the care of feeding the sheep [cf. John 21:15 ff.]; and to him also He handed over the keys of the kingdom of heaven, and upon him He promised to build his Church, and He testified that the gates of hell would not prevail against it [cf. Matt. 16:16 ff.]. But, because the enemy of the human race even until the end of the world does not abstain from sowing cockle [Matt. 13:25] over the good seed in the Church of the Lord, and therefore, lest perchance anyone with malignant zeal should by the instigation of the devil presume to make some alterations in and to draw conclusions regarding the integrity of the faith; and (lest) by reason of this your minds perhaps may seem to be disturbed, we have judged it necessary through our present epistle to exhort with tears that you should return to the heart of your mother the Church, and to send you satisfaction with regard to the integrity of faith.…” (Pope Pelagius II, Epistle 1, Quod ad dilectionem, writing to the Bishops of Istria, quoted in: Cardinal Manning, The Vatican Council and Its Definitions; p. 88 [A.D. 590])