Bede the Venerable — as excerpted in the Catena Aurea on Luke 3:15-17

“The Holy Spirit also may be understood by the word fire, for He kindles with love and enlightens with wisdom the hearts which He fills. Hence also the Apostles received the baptism of the Spirit in the appearance of fire. There are some who explain it, that now we are baptized with the Spirit, hereafter we shall be with fire, that as in truth we are now born again to the remission of our sins by water and the Spirit, so then we shall be cleansed from certain lighter sins by the baptism of purifying fire.”