Hilary of Poitiers — as excerpted in the Catena Aurea on John 4:19-24

“(ii. de Trin. c. 31) Or, by saying that God being a Spirit ought to be worshipped in spirit, He indicates the freedom and knowledge of the worshippers, and the uncircumscribed nature of the worship: according to the saying of the Apostle, Where the Spirit of the Lord is, there is liberty. (2 Cor. 3:17)”