Abud-Darda' (May Allah be pleased with him) said:
The Prophet (ﷺ) said, "He who defends the honour of his (Muslim) brother, Allah will secure his face against the Fire on the Day of Resurrection."[At-Tirmidhi]. (IT)
App reference (IT): Book 18, Hadith 18 (IT)
Arabic/English book reference (IT): Book 18, Hadith 1528 (IT)