Trinity and Holy Orders

They introduce God as a Being unknown; they suppose Christ to be unbegotten; and as to the Spirit, they do not admit that He exists. Some of them say that the Son is a mere man, and that the Father, Son, and Holy Spirit are but the same person, and that the creation is the work of God, not by Christ, but by some other strange power.

Be on your guard, therefore, against such persons. And this will be the case with you if you are not puffed up, and continue in intimate union with Jesus Christ our God, and the bishop, and the enactments of the apostles. He that is within the altar is pure, but he that is without is not pure; that is, he who does anything apart from the bishop, and presbytery, and deacons, such a man is not pure in his conscience.

Ignatius of Antioch
Epistle to the Trallians
Chapter VI – VII

The Trinity, the Orders, and the Flesh and Spirit

Study, therefore, to be established in the doctrines of the Lord and the apostles, that so all things, whatsoever ye do, may prosper both in the flesh and spirit; in faith and love; in the Son, and in the Father, and in the Spirit; in the beginning and in the end; with your most admirable bishop, and the well-compacted spiritual crown of your presbytery, and the deacons who are according to God. Be ye subject to the bishop, and to one another, as Jesus Christ to the Father, according to the flesh, and the apostles to Christ, and to the Father, and to the Spirit; that so there may be a union both fleshly and spiritual.

Ignatius of Antioch
Epistle to the Magnesians
Chapter XIII

Trinitarian Illustration

…being stones of the temple of the Father, prepared for the building of God the Father, and drawn up on high by the instrument of Jesus Christ, which is the cross, making use of the Holy Spirit as a rope, while your faith was the means by which you ascended, and your love the way which led up to God.

Ignatius of Antioch
Epistle to the Ephesians
Chapter IX

Trinitarian salutation

We wish you, brethren, all happiness, while you walk according to the doctrine of the Gospel of Jesus Christ; with whom be glory to God the Father and the Holy Spirit, for the salvation of His holy elect, after whose example the blessed Polycarp suffered, following in whose steps may we too be found in the kingdom of Jesus Christ!

Martyrdom of Polycarp
Chapter XXII