Musnad Ahmad 30:584

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from 'Abd al-Rahman ibn Hurmuz, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Let no one among you prevent his neighbor from placing a wooden beam on his wall." Then Abu Hurayrah said: "Why do I see you turning away from it? By Allah, I will certainly cast it between your shoulders."