Praise be to Allah.
Giving talaaq (divorce) three times at once is bid’ah, and goes against the aayah (interpretation of the meaning): “… When you divorce women, divorce them at their ‘iddah (prescribed periods)…” [al-Talaaq 65:1]. If a Muslim wants to divorce his wife, he should divorce her according to the Sunnah, which is to give one talaaq at a time when his wife is taahir (not menstruating) and he has not yet had intercourse with her following her period, or when it is clear that she is pregnant. According to the Shaafi’i madhhab and the majority of other madhhabs, giving three talaaqs at once counts as three separate talaaqs and is irrevocable, and the couple cannot remarry until the woman has been married to and divorced from another man. Other scholars say that three talaaqs given at once count as only one talaaq.And Allaah knows best.