"Not every intimate intercourse with the unconverted world is deemed lawful, by Calvinism, for it placed a barrier against the too unhallowed influence of this world by putting a distinct 'veto' upon three things, card playing, theatres, and dancing..."
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Many of you guessed this one. It was indeed from Abraham Kuyper's Lectures on Calvinism, Eerdmans, 1931), p. 73, (the second lecture, "Calvinism and Religion").