مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3114
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn ‘Abbas (رضي الله عنه) that he said. A woman sailed on the sea and vowed to fast for one month, then she died before she could fast. Her sister came to the Prophet (ﷺ) and told him about that and he told her to fast on her behalf.
Musnad Ahmad 3138Its isnad is saheeh, al-Bukhari (1953) and Muslim (1148)]