Saint Hilary of Poitiers on the Trinity

In De Trinitate, Hilary writes: Jesus "has commanded us to baptize in the name of the Father and of the Son and of the Holy Spirit (cf. Mt 28:19), that is, in the confession of the Author, of the Only-Begotten One and of the Gift.

The Author of all things is one alone, for one alone is God the Father, from whom all things proceed. And one alone is Our Lord Jesus Christ, through whom all things exist (cf. 1 Cor 8:6), and one alone is the Spirit (cf. Eph 4:4), a gift in all….

In nothing can be found to be lacking so great a fullness, in which the immensity in the Eternal One, the revelation in the Image, joy in the Gift, converge in the Father, in the Son and in the Holy Spirit".

— Pope Benedict XVI, General Audience, October 10, 2007