Ibn Mas'ud (May Allah be pleased with him) said:
The Prophet (ﷺ) said, "Shall I tell you what 'Al-'Adhu' (falsehood and slandering) is? It is calumny which is committed among the people."[Muslim].
App reference: Book 18, Hadith 28
Arabic/English book reference: Book 18, Hadith 1538