Gregory the Great — as excerpted in the Catena Aurea on Luke 3:3-6

“(20. in Ev.) Or, the valley when filled increases, but the mountains and hills when brought low decrease, because the Gentiles by faith in Christ receive fulness of grace, but the Jews by their sin of treachery have lost that wherein they boasted. For the humble receive a gift because the hearts of the proud they keep afar off.”