Luxury and religiousness help to harden the heart, and they give to the heart a peculiar hardness and callousness.
The rough man who swears at, and scorns God's mercy is hard in his way; but his hardness is like that of the rock which the blow of the hammer breaks in pieces.
The religiously hardened heart is like a lump of India rubber, which, hit it as you will, only flings back the stroke of the hammer.
The ancient battering ram, which would crush down stone walls and iron gates, was often baffled by bales of straw and bags of sand or other soft substances placed in front of the walls and gates.
It is this India rubber kind of hardness, this respectable, religious hardness of heart, which is so difficult to overcome, and which repels, which flings back, the blows of the gospel.
Jesus said: