St. Gregory of Nyssa

All that the Father is, we see revealed in the Son; all that is the Son’s is the Father's also; for the whole Son dwells in the Father, and he has the whole Father dwelling in himself… The Son who exists always in the Father can never be separated from him, nor can the Spirit ever be divided from the Son who through the Spirit works all things. He who receives the Father also receives at the same time the Son and the Spirit. It is impossible to envisage any kind of severance or disjunction between them: One cannot think of the Son apart from the Father, nor divide the Spirit from the Son. There is between the three a sharing and a differentiation that are beyond words and understanding.