Theophylact of Ohrid
Catena Aurea · Lukasevangelium 3
And many other things in his exhortation preached he unto the people. But Herod the tetrarch, being reproved by him for Herodias his brother Philip’s wife, and for all the evils which Herod had done, Added yet this above all, that he shut up John in prison.
For his exhortation was the telling of good things, and therefore is fitly called the Gospel.