ENOfficial
Narrated Ibn 'Abbas: Sa'd b. 'Ubadah asked the Messenger of Allah (ﷺ): My Mother has died and she could not fulfill her vow which she had taken. The Messenger of Allah (ﷺ) said: Fulfill it on her behalf.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا الْقَعْنَبِيُّ، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنْ عَبْدِ اللَّهِ بْنِ عَبَّاسٍ، : أَنَّ سَعْدَ بْنَ عُبَادَةَ، اسْتَفْتَى رَسُولَ اللَّهِ صلى الله عليه وسلم فَقَالَ : إِنَّ أُمِّي مَاتَتْ وَعَلَيْهَا نَذْرٌ لَمْ تَقْضِهِ . فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " اقْضِهِ عَنْهَا " .
sunnah.com