A man came to the Prophet ﷺ and said, "Messenger of Allah, teach me, and be brief."He said, "When you stand for your prayer, pray as though it were your farewell prayer. Do not speak words for which you will later have to apologize. And give up all hope in what people possess."
حدثنا محمد بن زياد حدثنا الفضيل بن سليمان حدثنا عبد الله بن عثمان بن خثيم حدثني عثمان بن جبير مولى أبي أيوب
جاء رجل إلى النبي ﷺ فقال يا رسول الله علمني وأوجز قال إذا قمت في صلاتك فصل صلاة مودع ولا تكلم بكلام تعتذر منه وأجمع اليأس عما في أيدي الناس
Sourcing, hasan. Ahmad reported it, 5/412, from the hadith of Ibn Khuthaym through this route, and a group narrated it from him. Busiri graded it daif because of Uthman bin Jubayr. It has corroborating narrations in Hakim, 4/326, 327, where he graded it sahih, and Dhahabi agreed with him, from the hadith of Saad bin Abu Waqqas. Diya Maqdisi also included it in Al-Mukhtarah from the hadith of Ibn Umar.