Sahih Muslim 110 a
Thabit b. Dahhak reported that he pledged allegiance to the Messenger of Allah (ﷺ) under the Tree, and verily the Messenger of Allah (ﷺ) observed:
He who took an oath of a religion other than Islam, in the state of being a liar, would became so, as he professed. He who killed himself with a thing would be tormented on the Day of Resurrection with that very thing. One is not obliged to offer votive offering of a thing which is not in his possession.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا مُعَاوِيَةُ بْنُ سَلاَّمِ بْنِ أَبِي سَلاَّمٍ الدِّمَشْقِيُّ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، أَنَّ أَبَا قِلاَبَةَ، أَخْبَرَهُ أَنَّ ثَابِتَ بْنَ الضَّحَّاكِ أَخْبَرَهُ أَنَّهُ، بَايَعَ رَسُولَ اللَّهِ صلى الله عليه وسلم تَحْتَ الشَّجَرَةِ وَأَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏
"‏ مَنْ حَلَفَ عَلَى يَمِينٍ بِمِلَّةٍ غَيْرِ الإِسْلاَمِ كَاذِبًا فَهُوَ كَمَا قَالَ وَمَنْ قَتَلَ نَفْسَهُ بِشَىْءٍ عُذِّبَ بِهِ يَوْمَ الْقِيَامَةِ وَلَيْسَ عَلَى رَجُلٍ نَذْرٌ فِي شَىْءٍ لاَ يَمْلِكُهُ ‏"‏ ‏.‏