I was with Ibn ʿUmar when a man asked him, "I have vowed to fast every Tuesday or Wednesday throughout my life and if the day of my fasting coincided with the day of Nahr (the first day of ʿId-al- Adha), (What shall I do?)" Ibn ʿUmar said, "Allah has ordered the vows to be fulfilled, and we are forbidden to fast on the day of Nahr." The man repeated his question and Ibn ʿUmar repeated his former answer, adding nothing more.
أَنْ أَصُومَ كُلَّ يَوْمِ ثَلاَثَاءَ أَوْ أَرْبِعَاءَ مَا عِشْتُ فَوَافَقْتُ هَذَا الْيَوْمَ يَوْمَ النَّحْرِ فَقَالَ أَمَرَ اللَّهُ بِوَفَاءِ النَّذْرِ وَنُهِينَا أَنْ نَصُومَ يَوْمَ النَّحْرِ فَأَعَادَ عَلَيْهِ فَقَالَ مِثْلَهُ لاَ يَزِيدُ عَلَيْهِ