These three witnesses are one, as John said: 'The water, the blood, and the Spirit' (I Jn. 5:8). One in the mystery, not in nature. The water, then, is a witness of burial, the blood is a witness of death, the Spirit is a witness of life. If, then, there be any grace in the water, it is not from the nature of water, but from the presence of the Holy Spirit.
Theological and Dogmatic Works (The Fathers of the Church, Volume 44) (ed. CUA Press, 2010) - ISBN: 9780813211442