The devil is most happy when he can snatch from a servant of God true joy of the Spirit. He carries dust with him to throw into the smallest chinks of conscience and thus soil one’s mental candor and purity of life.

But if joy of the Spirit fills the heart, the serpent shoots his deadly venom in vain.

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Gender-neutral paraphrase:

The devil is most happy to snatch from a servant of God true joy of the Spirit. The devil carries supplies of dust to throw into the smallest chinks of conscience and thus soil one’s mental candor and purity of life.

But if joy of the Spirit fills the heart, the serpent’s deadly venom is shot in vain.