Musnad Ahmad 271:0

The Hadith of Hawdhah al-Ansari, from his grandfather: The Messenger of Allah (ﷺ) said: "Do not be people who follow others, saying: 'If the people do good, we will do good, and if they do wrong, we will do wrong.' Rather, discipline yourselves: if the people do good, do good, and if they do wrong, do not do wrong."