The Messenger of Allah ﷺ went out one day and prayed over the people of Uhud the prayer for the dead. Then he turned toward the pulpit and said, "I am your forerunner, and I am a witness over you."
أخبرنا قتيبة قال حدثنا الليث عن يزيد عن أبي الخير
أن رسول الله ﷺ خرج يوما فصلى على أهل أحد صلاته على الميت ثم انصرف إلى المنبر فقال إني فرط لكم وأنا شهيد عليكم
Bukhari narrated it in Riqaq, chapter on beware of the flowers of this world and competing for them, hadith no. 6426, and Muslim narrated it in Fadail, chapter on establishing the pool of our Prophet and its descriptions, hadith no. 2296, from Qutayba, with the same wording, and it is in Kubra, hadith no. 2081.