Sahih Bukhari
Judgments (Ahkaam)
Volume: 009 / Book Number: 089 / Hadith Number: 260
Narrated 'Abdur-Rahman bin Samura:
The Prophet said, "O 'Abdur-Rahman! Do not seek to be a ruler, for if you are given authority on your demand then you will be held responsible for it, but if you are given it without asking (for it), then you will be helped (by Allah) in it. If you ever take an oath to do something and later on you find that something else is better, then you should expiate your oath and do what is better."