Does backbiting people break the fast in Ramadaan?
Backbiting does not break the fasting person's fast. (Backbiting) is to mention about an individual that which he detests. It is a sin due to Allah's statement,
وَلَا يَغْتَب بَّعْضُكُم بَعْضًا
And do not backbite one another. (Al Hujuraat: 12)
Likewise is the case for slander, verbal abuse, cursing and lying. Each of these does not break the fast but are sins that the fasting person and other than him must beware of and avoid. Each of these (although they do not break the fast), harm the fast and decrease its reward due to the statement of the Prophet ﷺ,
من لم يدع قول الزور والعمل به فليس لله حاجة في أن يدع طعامه وشرابه
Whoever does not give up lying speech, acting in accordance to it and (acting) ignorantly, then Allah is in no need that they abandon their food and drink.
[Collected by Imaam Al-Bukhaari in his Saheeh]
And also due to the statement of the Prophet ﷺ
الصيام جُنة فإذا كان يوم صوم أحدكم فلا يرفث ولا يصخب، فإن سابه أحد أو قاتله، فليقل: إني صائم
Fasting is a shield; during the day in which one of you is fasting he should not behave in an obscene manner nor shout in rage. And if someone verbally abuses him or tries to fight him he should say, "I am fasting"
- Fiqh and Fataawa