Pseudo-Chrysostom — as excerpted in the Catena Aurea on Matthew 3:11-12

“But since no one can give a benefit more worthy than he himself is, nor to make another what himself is not, he adds, He shall baptize you with the Holy Ghost and with fire. John who is carnal cannot give spiritual baptism; he baptizes with water, which is matter; so that he baptizes matter with matter. Christ is Spirit, because He is God; the Holy Ghost is Spirit, the soul is spirit; so that Spirit with Spirit baptizes our spirit. The baptism of the Spirit profits as the Spirit enters and embraces the mind, and surrounds it as it were with an impregnable wall, not suffering fleshly lusts to prevail against it. It does not indeed prevail that the flesh should not lust, but holds the will that it should not consent with it. And as Christ is Judge, He baptizes in fire, i. e. temptation; mere man cannot baptize in fire. He alone is free to tempt, who is strong to reward. This baptism of tribulation burns up the flesh that it does not generate lust, for the flesh does not fear spiritual punishment, but only such as is carnal. The Lord therefore sends carnal tribulation on his servants, that the flesh fearing its own pains, may not lust after evil. See then how the Spirit drives away lust, and suffers it not to prevail, and the fire burns up its very roots.”