Musnad Abu Ya'la al-Mawsili 245:6

Sulayman ibn Abd al-Jabbar Abu Ayyub al-Raqqi narrated to us, Abu Asim narrated to us, from Ibn Jurayj, from Muhammad ibn al-Munkadir, from a man, from Mu'awiyah, that he saw the Messenger of Allah (may Allah bless him and grant him peace) eat *liba'* (beestings/colostrum), then he prayed and did not perform ablution.