Abu Hurairah (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "When two persons indulge in abusing each other, the beginner will be the sinner so long as the oppressed does not transgress the limits."[Muslim]. (DE)
App reference (DE): Book 18, Hadith 51 (DE)
Arabic/English book reference (DE): Book 18, Hadith 1561 (DE)