What is the expiation for someone who swore by the Qur'an to quit smoking, then broke their oath, then swore by divorce that they would not swear by the Qur'an again, then forgot and swore by the Qur'an again about smoking?

The question includes two issues:

1. Repeatedly swearing by the Qur’an to quit smoking, then breaking the oath: You are obligated to offer a single expiation for an oath (kaffarat yamin), unless the wording of the oath implies repetition, or you intended multiple expiations for multiple oaths, or the swearing was repeated after breaking the previous oath. In these cases, the expiations are multiplied.

2. Swearing by divorce not to swear by the Qur’an, then swearing by it forgetfully: The preponderant opinion (rajih) with us is that no divorce is binding upon you. This is the apparent view of the Shafi’i madhhab and the choice of Shaykh al-Islam Ibn Taymiyyah.

We advise you to strive against your self to quit smoking due to its harms.