Poverty of goods is easy to cure, poverty of soul impossible.

[La pauvreté des biens, est aisée à guerir, la pauvreté de l’ame, impossible.]

Michel de Montaigne (1533-1592) French essayist

Essays, Book 3, ch. 10 (3.10), “Of Managing the Will [De mesnager sa volonté]” (1586) [tr. Frame (1943)]
    (Source)

In context, "poverty of the soul" is given by Montaigne, not as a moral failing, but as the soul-felt sense of poverty, of not having enough, of needing to attain more.

The essay, including this passage, first appeared in the 2nd ed. (1588).

(Source (French)). Alternate translations:

Want of goods may easilie be cured, but the poverty of the mind, is incurable.
[tr. Florio (1603)]

The Want of Goods, is easily repair'd; but the Poverty of the Soul is irreparable.
[tr. Cotton (1686)]

The poverty of goods is easily cured; the poverty of the soul is irreparable.
[tr. Cotton/Hazlitt (1877)]

Poverty in worldly goods is easy to cure; poverty of the soul, impossible.
[tr. Ives (1925)]

To cure poverty of possessions is easy: poverty of soul impossible.
[tr. Screech (1987)]

Poverty of possessions may easily be cured, but poverty of soul never.
[Source]