Sahih Muslim Book 18, Hadith Number 4267.

Sa’d b. Ibrahim reported: I asked Qasim b. Muhammad about a person who had three dwelling houses and he willed away the third part of every one of these houses; he (Qasim b. Muhammad) said: All of them could be combined in one house; and then said: ‘Aisha informed me that Allah’s Messenger (may peace be upon him) said: He who did any act for which there is no sanction from our behalf, that is to be rejected.