One should not seek among others the truth that can be easily gotten from the Church. For in her, as in a rich treasury, the apostles have placed all that pertains to truth, so that everyone can drink this beverage of life. She is the door of life.
Irenaeus of LyonsAnd when we come to refute them, we shall show in its fitting place that this class of men [i.e., the gnostics] has been instigated by satan to a denial of that baptism which is regeneration to God, and thus to a denial of the whole faith [by denying all physical aspects of spirituality, including the incarnatian and bodily resurrection of Jesus].
Irenaeus of LyonsOthers of them employ outward marks ... They style themselves Gnostics. They also possess images, some of them painted and others formed from different kinds of material. They maintain that a likeness of Christ was made by Pilate at that time when Jesus lived among them. They crown these images, and set them up along with the images of the philosophers of the world, such as Pythagoras, Plato, and Aristotle, and the rest. They have also other modes of honoring these images just like the Gentiles.
Irenaeus of LyonsSuppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, in that case, to follow the course of the tradition which they handed down to those to whom they did commit the Churches?
Irenaeus of Lyons