Does divorce take effect if I drink tea by mistake after swearing to abstain from it, following my oath of divorce to quit cigarettes?

If you swore an oath of divorce unintentionally, and your tongue merely slipped, then it is considered a 'laghw' (unintentional, vain oath) and does not result in divorce or require expiation. The Shafi'is hold that a slip of the tongue in an oath without intention is not binding and does not require expiation, unlike oaths of divorce, manumission (of slaves), or 'ila' (oath to abstain from sexual relations with one's wife), for which the apparent meaning is not disbelieved. Furthermore, using oaths as a means to abandon sins is not a sound approach; the straight path is to seek Allah's help and offer sincere repentance.