From the Scholia on the Incarnation of Christ, section 36:
Saint Paul sets forth to us the Saving Passion, for he saith at one time, By the Grace of God for all tasted He death and also, For I delivered to you in the first place that which I too received, that Christ died for our sins according to the Scriptures and that He was buried and that He rose again the third day: moreover the most wise Peter also saith, Forasmuch as Christ suffered for us in the Flesh. Seeing therefore we believe that One is our Lord Jesus Christ, i. e. God the Word beheld in human form or made man as we, in what manner can we attribute Passion to Him and still hold Him impassible, as God?
The Passion therefore will belong to the Economy, God the Word esteeming as His own the things which pertain to His own Flesh, by reason of the Ineffable Union, and remaining external to suffering as far as pertains to His own Nature, for God is Impassible. And no wonder, since we see that the soul itself of a man, if its body suffer somewhat, remains external to the suffering as far as belongs to its own nature, yet is it not conceived of as external to suffering, in that the body which suffers is its very own: and albeit it be impalpable and simple, yet is that which suffers not foreign to it. Thus will you understand of Christ too the Saviour of all.