Musnad Ahmad 1286:3

'Abd al-Malik ibn 'Amr narrated to us, Zuhayr ibn Muhammad narrated to us, from Zayd, from 'Amr ibn Mu'adh al-Ansari, who said: A beggar stood at their door, and his grandmother, Hawwa', said to them, "Feed him dates." They said, "We do not have any." She said, "Then give him some *sawiq* (barley meal) to drink." They said, "We are amazed at you; how can we feed him what we do not have?" She said, "I heard the Messenger of Allah, may Allah bless him and grant him peace, say: 'Do not turn away the beggar, even if with a burnt hoof.'"