Al-Rabia’ reported: Ibn Sirin, may Allah have mercy on him, said, “It is an act of wrong against your brother that you mention what you know is evil about him, while you are silent upon his good.”
Source: Ṣifat al-Ṣafwah 2/145
عن الربيع عن ابن سيرين قال رحمه الله ظلم لأخيك أن تذكر منه أسوأ ما تعلم وتكتم خيره
2/145 صفة الصفوة