Thus, in fact, the difference [in observing] the fast establishes the harmony of [our common] faith. For neither could Anicetus persuade Polycarp to forego the observance [in his own way], inasmuch as these things had been always [so] observed by John the disciple of our Lord, and by other apostles with whom he had been conversant; nor, on the other hand, could Polycarp succeed in persuading Anicetus to keep [the observance in his way], for he maintained that he was bound to adhere to the usage of the presbyters who preceded him.
…so that they parted in peace one from the other, maintaining peace with the whole Church, both those who did observe [this custom] and those who did not.
Irenaeus of Lyons
Lost Writings
Fragment III