Narrated Ibn 'Abbas:

A woman from the tribe of Juhaina came to the Prophet and said, "My mother had vowed to perform Hajj but she died before performing it. May I perform Hajj on my mother's behalf?" The Prophet replied, "Perform Hajj on her behalf. Had there been a debt on your mother, would you have paid it or not? So, pay Allah's debt as He has more right to be paid."

حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ أَبِي بِشْرٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ أَنَّ امْرَأَةً، مِنْ جُهَيْنَةَ جَاءَتْ إِلَى النَّبِيِّ ﷺ فَقَالَتْ إِنَّ أُمِّي نَذَرَتْ أَنْ تَحُجَّ، فَلَمْ تَحُجَّ حَتَّى مَاتَتْ أَفَأَحُجُّ عَنْهَا قَالَ " نَعَمْ. حُجِّي عَنْهَا، أَرَأَيْتِ لَوْ كَانَ عَلَى أُمِّكِ دَيْنٌ أَكُنْتِ قَاضِيَةً اقْضُوا اللَّهَ، فَاللَّهُ أَحَقُّ بِالْوَفَاءِ ".