Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:2378ʿAbdullāh b. Saʿīd > Ḥafṣ > ʿUbaydullāh > Nāfiʿ > Ibn ʿUmar > ʿUmar

[Machine] I said, "O Messenger of Allah, indeed I made a vow in the time of ignorance, then Islam came." He said, "Fulfill your vow."  

الدارمي:٢٣٧٨حَدَّثَنَا عَبْدُ اللَّهِ بْنُ سَعِيدٍ حَدَّثَنَا حَفْصٌ حَدَّثَنَا عُبَيْدُ اللَّهِ عَنْ نَافِعٍ عَنْ ابْنِ عُمَرَ عَنْ عُمَرَ قَالَ

قُلْتُ يَا رَسُولَ اللَّهِ إِنِّي نَذَرْتُ نَذْرًا فِي الْجَاهِلِيَّةِ ثُمَّ جَاءَ الْإِسْلَامُ قَالَ فِ بِنَذْرِكَ