Sa'id bin Jubayr narrates from Ibn Abbas (may Allah be pleased with him) that a woman set out on a sea voyage and vowed that if Allah saved her, she would fast for a month. Allah saved her, but she died before fasting. Her daughter or her sister came, and the Prophet (peace and blessings be upon him) "gave the order to fast" on her behalf.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النذور / 20148