First Council of Nicaea, Canon IX

If any presbyters have been advanced without examination, or if upon examination they have made confession of crime, and men acting in violation of the canon have laid hands upon them, notwithstanding their confession, such the canon does not admit; for the Catholic Church requires that [only] which is blameless.

Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.