Abu Dawud Book 23, Hadith Number 3904.
Chapter : Taking omens.
Narated By Abu Hurairah : The Prophet (PBUH) said: There is no ghoul.
Abu Dawud said: Malik was asked about the meaning of his saying: There is no safar. He replied: The people in pre-Islamic Arabia used to make the month of ;afar lawful (for war). They made it lawful in one year and unlawful in another year. The Prophet (may peace be upon him) said: There is no safar.