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.
أَخْبَرَهُ أَنَّهُ بَايَعَ رَسُولَ اللَّهِ ﷺ تَحْتَ الشَّجَرَةِ وَأَنَّ رَسُولَ اللَّهِ ﷺ 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