Sahih Muslim | Book 15 | Hadith Number 4062

Narrated by Abd al-Rahman b. Samura
Abd al-Rahman b. Samura reported that Allah's Messenger (may peace be upon him) said to me: Abd al-Rahman b. Samura, don't ask for authority for if it is granted to you for asking for it, you would be commissioned for it (without having the support of Allah), but if you are granted it without your asking for it. You would be helped (by Allah) in it. And when you take an oath and find something else better than that, expiate for (breaking) your oath, and do that which is better. This hadith has also been transmitted on the authority of Ibn Farrukh.