Maliks Muwatta Book 36, Hadith Number 32.
Section : Judgement on Benefiting Neighbours.
Malik related to me from Ibn Shihab from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, “No one should prevent his neighbour from fixing a wooden peg in his wall.” Then Abu Hurayra said, “Why do I see you turning away from it? By Allah! I shall keep on at you about it.”