Christian Texts and History • Re: Against Polycarp

Thereupon Victor, who presided over the church at Rome, immediately attempted to cut off from the common unity the parishes of all Asia, with the churches that agreed with them, as heterodox; and he wrote letters and declared all the brethren there wholly excommunicate. But this did not please all the bishops. And they besought him to consider the things of peace, and of neighborly unity and love. Words of theirs are extant, sharply rebuking Victor. Among them was Irenaeus, who, sending letters in the name of the brethren in Gaul over whom he presided, maintained that the mystery of the resurrection of the Lord should be observed only on the "Lord's day" namely Easter. He fittingly admonishes Victor that he should not cut off whole churches of God which observed the tradition of an ancient custom.

— Eusebius, Book V Chapter 24 see Cantalamessa 1993, pp. 33–37