Oaths and Vows (Kitab Al-Aiman Wa Al-Nudhur)
Dawud :: Book 21 : Hadith 3242
Narrated AbuHurayrah:
The Prophet (peace_be_upon_him) said: Do not swear by your fathers, or by your mothers, or by rivals to Allah; and swear by Allah only, and swear by Allah only when you are speaking the truth.