III. Only by imitating his predecessor will he regain Leo's confidence: the assent of the bishops is declared null and void.
Let him realize what a man he has succeeded, and expelling all the spirit of pride let him imitate Flavian's faith, Flavian's modesty, Flavian's humility, which has raised him right to a confessor's glory. If he will shine with his virtues, he will merit all praise, and in all quarters he will win an abundance of love not by seeking human advancement but by deserving Divine favour. And by this careful course I promise he will bind my heart also to him, and the love of the Apostolic See, which we have ever bestowed on the church of Constantinople, shall never be violated by any change.
Because if sometimes rulers fall into errors through want of moderation, yet the churches of Christ do not lose their purity. But the bishops' assents, which are opposed to the regulations of the holy canons composed at Nicæa in conjunction with your faithful Grace, we do not recognize, and by the blessed Apostle Peter's authority we absolutely dis-annul in comprehensive terms, in all ecclesiastical cases obeying those laws which the Holy Ghost set forth by the 318 bishops for the pacific observance of all priests in such sort that even if a much greater number were to pass a different decree to theirs, whatever was opposed to their constitution would have to be held in no respect.
Source: Letters (New Advent)