Abu Dawud
The Office Of The Judge
Book Number: 018 / Hadith Number: 3587
Narated By Abu Hurairah : The Prophet (pbuh) said: Conciliation between Muslims is permissible. The narrator Ahmad added in his version: "except the conciliation which makes lawful unlawful and unlawful lawful." Sulayman ibn Dawud added: The Apostle of Allah (pbuh) said: Muslims are on (i.e. stick to) their conditions.