"Whoever makes a vow and does not state it specifically, the expiation (for such a vow) is the expiation for breaking an oath. "  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ نَذَرَ نَذْرًا وَلَمْ يُسَمِّهِ فَكَفَّارَتُهُ كَفَّارَةُ يَمِينٍ  

"Whoever makes a vow and does not state it specifically, the expiation (for such a vow) is the expiation for breaking an oath. Whoever makes a vow and is not able to fulfill it, the expiation for that is the expiation for breaking an oath. Whoever makes a vow and is able to fulfill it, let him do so."  

عَنِ النَّبِيِّ ﷺ قَالَ مَنْ نَذَرَ نَذْرًا وَلَمْ يُسَمِّهِ فَكَفَّارَتُهُ كَفَّارَةُ يَمِينٍ وَمَنْ نَذَرَ نَذْرًا لَمْ يُطِقْهُ فَكَفَّارَتُهُ كَفَّارَةُ يَمِينٍ وَمَنْ نَذَرَ نَذْرًا أَطَاقَهُ فَلْيَفِ بِهِ