Musnad Ahmad 26:782

'Affan narrated to us, Hammad narrated to us, he said: 'Asim ibn Bahdalah informed us, from Abu Wa'il, from Ibn Mas'ud, that the Messenger of Allah (may Allah bless him and grant him peace) said: "I am your forerunner at the Basin (al-Hawd). I will contend with men, and I will be overcome regarding them. I will surely say: 'O Lord, my little companions, my little companions!' It will be said to me: 'Indeed, you do not know what they innovated after you.'"