Sahih Muslim Book 5, Hadith Number 2331.

Chapter : It is forbidden to pay Zakat to the Messenger of Allah (may peace be upon him) and Banu Hashim and Banu Muttalib.

‘Abida narrated from ‘Ali that he made a mention of the Khwarij (and in this connection) said that there would be a person among them with a defective hand, (or with a short hand) or a fleshy hand. If you were to exercise restraint, I would tell you what Allah has promised to those who would kill them on the order of Muhammad (may peace be upon him). I (the narrator) said to him: Did you hear it from Muhammad: (may peace be upon him)? He (Hadrat ‘Ali) said: Yes, by the Lord of the Ka’ba; Yes, by the Lord of the Ka’ba; yes, by the Lord of the Ka’ba.