Sahih Bukhari Volume 9, Book 93, Hadith 7148

حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا جَرِيرُ بْنُ حَازِمٍ، عَنِ الْحَسَنِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ سَمُرَةَ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ يَا عَبْدَ الرَّحْمَنِ لاَ تَسْأَلِ الإِمَارَةَ، فَإِنَّكَ إِنْ أُعْطِيتَهَا عَنْ مَسْأَلَةٍ وُكِلْتَ إِلَيْهَا، وَإِنْ أُعْطِيتَهَا عَنْ غَيْرِ مَسْأَلَةٍ أُعِنْتَ عَلَيْهَا، وَإِذَا حَلَفْتَ عَلَى يَمِينٍ فَرَأَيْتَ غَيْرَهَا خَيْرًا مِنْهَا، فَكَفِّرْ يَمِينَكَ، وَأْتِ الَّذِي هُوَ خَيْرٌ ‏"‏‏

Narrated By '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."