Augustine of Hippo

Let us hold firmly that Father and Son and Holy Spirit in their own proper nature, their proper substance, are together and equally invisible. We believe them to be together and equally immortal, together and equally imperishable. There is one place where the apostle states all these things simultaneously, "Now to the king of ages, immortal, invisible, imperishable, to the only God, be honor and glory for ever and ever. Amen."