What is the ruling of the Shariah on a wife withholding herself from her husband until he quits smoking?

If the wife swore not to allow her husband intimacy until he quits smoking, then she has erred. She must allow him intimacy, and she owes an expiation for breaking an oath (kaffarat yamin). However, if it was the husband who swore an oath, then he owes an expiation for breaking an oath if he has intercourse with his wife before she quits smoking. The wife has a right to intimacy according to the husband's capacity and her need.