A feast is approaching which is the most solemn and awe-inspiring of all feasts.... What is it? The birth of Christ according to the flesh. In this feast namely Epiphany, holy Easter, Ascension and Pentecost have their beginning and purpose. For if Christ hadn't been born according to the flesh, he wouldn't have been baptised, which is Epiphany. He wouldn't have been crucified, which is Easter. He wouldn't have sent the Spirit, which is Pentecost. So from this event, as from some spring, different rivers flow-these feasts of ours are born.Concerning Blessed Philogonius, in Mayer and Adam John Chrysostom, London:2000, p.191
even in one's very bearing and tone of voice: not lowly towards one, and rude towards another; be lowly towards all men, be he friend or foe, be he great or small.Ephesians Commentary
our tendency to skip over this issue and go directly to that of the work of the Spirit is unbalanced and unhelpful - the work which the Spirit does is directly dependent on who the Spirit is.Double Procession, 423.
Nor, by the way, can we say that the Holy Spirit does not proceed from the Son as well; it is not without point that the same Spirit is called the Spirit of the Father and of the Son.The Trinity (Brooklyn: New City Press, 1991), 174
If my understanding is correct, then both the procession and the sending mentioned in the verse take place in history. Now, that understanding does not make the verse irrelevant to the doctrine of eternal procession, for as we have seen it is legitimate to find an analogy between the historical and the eternal relationships among the persons of the Trinity. But if both the procession and the sending of John 15:26 take place in time, that would support, by analogy, the view that the Spirit's eternal procession is from both Father and Son.Systematic Theology