The Messenger of Allah ﷺ said, "When you hear..." and Musa said, "When a man says, 'The people are ruined,' he is the one who has ruined them most."
حدثنا القعنبي عن مالك ح و حدثنا موسى بن إسمعيل حدثنا حماد عن سهيل بن أبي صالح عن أبيه
أن رسول الله ﷺ قال إذا سمعت وقال موسى إذا قال الرجل هلك الناس فهو أهلكهم
Muslim narrated it in the Book of Righteousness and Kinship Ties, Chapter: The Prohibition of Saying, "The people are ruined," hadith no. 2623, from the hadith of Hammad bin Salama, transmitted through him. It is also found in Muwatta (Yahya) 2/984, from Suhayl, transmitted through him.