(32) باب مَنْ نَذَرَ أَنْ يَصُومَ أَيَّامًا فَوَافَقَ النَّحْرَ أَوِ الْفِطْرَ
Narrated Ziyad bin Jubair:
I was with Ibn `Umar 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 `Id-al- Adha), (What shall I do?)" Ibn `Umar 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 `Umar repeated his former answer, adding nothing more.
Reference: Sahih al-Bukhari 6706
In-book reference: Book 83, Hadith 83
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 78, Hadith 697