Shaykh ‘Abd Al-‘Azeez Ibn Bāz [رحمه الله] said:

❝Backbiting does not cause a fasting person to break his fast and likewise is cursing, swearing and lying, all of these things do not cause a fasting person to break his fast.

However, they are sins which are obligatory to be warned against and kept away from by the fasting person and other than him. These actions wound the fast and decrease its reward.❞

[Majmoo Al-Fatawa, (15/320) | Translated By Abbas Abu Yahya Miraath Al-Anbiyya]