Sahih Bukhari
Oaths and Vows
Volume: 008 / Book Number: 078 / Hadith Number: 621
Narrated Abu Huraira:
The Prophet said, "We (Muslims) are the last in the world, but will be foremost on the Day of Resurrection." Allah's Apostle also said, "By Allah, if anyone of you insists on fulfilling an oath by which he may harm his family, he commits a greater sin in Allah's sight than that of dissolving his oath and making expiation for it."