Musnad Ahmad 31:551

'Abd al-Razzaq narrated to us, Malik narrated to us, from Ayyub ibn Habib, that he heard Abu al-Muthanna say: I heard Marwan asking Abu Sa'id al-Khudri: "Did you hear the Messenger of Allah, may Allah bless him and grant him peace, forbidding blowing into a drink?" He said: "Yes." He said: A man said: "But I do not quench my thirst, O Messenger of Allah, in one breath." He said: "Then remove the cup from your mouth, then breathe." He said: "I see dirt in it." He said: "Then pour it out."