What must a person do who sincerely swore by divorce to quit smoking, then returned to it, and this happened to him several times, and he is currently smoking?

Smoking is forbidden, and a conditional divorce takes effect when the condition is met. If you repeatedly swore by divorce to quit smoking, and then returned to it three or more times, intending divorce, then your wife has become irrevocably divorced (Bainunah Kubra). However, if you swore once to quit smoking, and then returned to it repeatedly, your oath is dissolved with the first breach, and no divorce occurs thereafter unless you swear again. If your divorces did not reach three, you may reconcile with your wife.