Is it permissible for a smoker to swear by Allaah that he will not smoke, and say “May the curse of Allaah be on me if I go back to smoking”? Because he cannot find any other means of making himself give it up. Or is this wrongful speech? 

Praise be to Allaah. 

We put this question to Shaykh Muhammad ibn Saalih
al-‘Uthaymeen, may Allaah preserve him, who answered as follows:

  He should not swear an oath to give up
smoking, or pray for himself to be cursed. Allaah says (interpretation
of the meaning):

“They swear by Allaah their strongest oaths, that if only you
would order them, they would leave (their homes for fighting in Allaah’s
Cause). Say:
‘Swear you not; (this) obedience (of yours) is known (to be false). Verily,
Allaah knows well what you do.’” [al-Noor 24:53]

  Question: But this [aayah]
has to do with the munaafiqeen (hypocrites), and our friend is sincere.

  Answer: This [ayah] is general [in meaning]. Every person who
wants to worship Allaah should not swear an oath concerning his worship;
let him strive of his own free will, not under compulsion.

  Question: so this way is wrong and he will be sinning if he does
it?

  Answer: No, what is denounceable is the fact that he is trying
to confirm something through this oath.

  Question: So we can say that this is an action which is not prescribed
in Islam?

  Answer: Yes, undoubtedly. And Allaah knows best.