"Take note of those who hold heterodox opinions on the grace of Jesus Christ, which has come to us, and see how contrary their opinions are to the mind of God. . . . They abstain from the Eucharist and from prayer, because they do not confess that the Eucharist is the Flesh of our Savior Jesus Christ, Flesh which suffered for our sins and which the Father, in His goodness, raised up again. They who deny the gift of God are perishing in their disputes." - Saint Ignatius of Antioch (died early 2nd Century)
"Those indeed, who belong to God and to Jesus Christ—they are with the bishop. And those who repent and come to the unity of the Church—they too shall be of God. . . . Do not err my brethren: if anyone follow a schismatic, he will not inherit the Kingdom of God. . . . Take care, then, to use one Eucharist, so that whatever you do, you do according to God: for there is one flesh of our Lord Jesus Christ, and one cup in the union of His Blood; one altar as there is one bishop with the presbytery and my fellow servants, the deacons." - Saint Ignatius of Antioch (died early 2nd Century)
"...although all heretics want to be called 'Catholic,' when a stranger inquires where the Catholic Church meets, none of the heretics would dare to point out his own basilica or house". - Saint Augustus 397