Canon 7 of the 2nd Ecumenical Council
âThose who from heresy turn to orthodoxy, and to the portion of those who are being saved, we receive according to the following method and custom: Arians, and Macedonians, and Sabbatians, and Novatians, who call themselves Catharia or Aristeri, and Quarto-decimans or Tetradites, and Apollinarians, we receive, upon their giving a written renunciation of their errors and anathematize every heresy which is not in accordance with the Holy, Catholic, and Apostolic Church of God. Thereupon, they are first sealed or anointed with the holy oil upon the forehead, eyes, nostrils, mouth, and ears; and when we seal them, we say, âThe seal of the gift of the Holy Ghost.â But EunomiansâŚ, Montanists, Phrygians, and Sabellians, and other heresiesâŚall theseâŚwe receive as heathenâŚâ
Canon 8 Council of Arles in 314.
âIf anyone shall come from heresy to the Church, they shall ask him to say the creed; and if they shall perceive that he was baptized into the Father, and the Son, and the Holy Ghost, he shall have a hand laid on him only that he may receive the Holy Ghost. But if in answer to their questioning he shall not answer this Trinity, let him be baptized.â
Considered ecumenical by Augustine, since I am sure cherry picked quotes by him will follow.
De Baptismo contra Donatistas, where he says : âThe question relating to re-baptism was decided against Cyprian, in a full council of the whole Churchâ (plenarium concilium, concilium universae Ecclesiae).