It was related on the authority of Abu Sa'id Sa'd bin Malik bin Sinan al-Khudri (ra) that the Messenger of Allah (sas) said:

There should be neither harming nor reciprocating harm.

(A excellent hadith which Ibn Majah, Al-Daraqutni and others related as of sound isnad, but which Malik related in his Muwatta' as of broken isnad, from 'Amr bin Yahya, from his father, from the Prophet (sas) but dropping (the name of) Abu Sa'id. This hadith has lines of transmission which strengthen one another (so that it may be regarded as of sound isnad).)