Sa'id bin Jubayr (may Allah have mercy on him) narrates from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that a man came to the Prophet (peace and blessings be upon him) and said: My sister vowed to perform Hajj, but she has died. He (peace and blessings be upon him) said: "If she had owed a debt, would you have paid it?" He said: Yes. He said: "Then fulfil what is owed to Allah, for He is more deserving of fulfilment."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9853