II. Let him be watchful against heresy and send frequent reports to Rome.
Take heed, then, dearly beloved brother, lest any trace of either Nestorius' or Eutyches' error be found in God's people: because “no one can lay any foundation except that which is laid, which is Christ Jesus;” who would not have reconciled the whole world to God the Father, had He not by the regeneration of Faith adopted us all in the reality of our flesh. Whenever, therefore, opportunities arise which you can use for writing, brother, even as you necessarily and in accordance with custom have done in sending a report of your ordination to us by our sons, Daniel the presbyter and Timothy the deacon, so continue to act at all times and send us, who will be anxious for them, as frequent accounts as possible of the progress of peace, in order that by regular intercourse we may feel that “the love of God is shed abroad in our hearts through the Holy Ghost, which is given unto us.” Dated the 18th of August, in the consulship of Magnus and Apollonius (460).
Source: Letters (New Advent)