Narrated Ibn `Abbas: A woman came to the Prophet (ﷺ) and said, "My mother vowed to perform the Hajj but she died before performing it. Should I perform the Hajj on her behalf?" He said, "Yes! Perform the Hajj on her behalf. See, if your mother had been in debt, would you have paid her debt?" She said, "Yes." He said, "So you should pay what is for Him as Allah has more right that one should fulfill one's obligations to Him. "
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ امْرَأَةً، جَاءَتْ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَتْ إِنَّ أُمِّي نَذَرَتْ أَنْ تَحُجَّ فَمَاتَتْ قَبْلَ أَنْ تَحُجَّ أَفَأَحُجَّ عَنْهَا قَالَ " نَعَمْ حُجِّي عَنْهَا، أَرَأَيْتِ لَوْ كَانَ عَلَى أُمِّكِ دَيْنٌ أَكُنْتِ قَاضِيَتَهُ ". قَالَتْ نَعَمْ. فَقَالَ " فَاقْضُوا الَّذِي لَهُ، فَإِنَّ اللَّهَ أَحَقُّ بِالْوَفَاءِ ".
sunnah.com