Language:
كتاب الصلاة
8  
Prayers (Salat)
(32)
Chapter: What has been said about (facing) the Qiblah (Kabah at Makkah) and wherever considered that there was no need to repeat the Salat (prayer) if someone offered prayers by mistake facing a direction other than that of the Qiblah
(32)
بَابُ مَا جَاءَ فِي الْقِبْلَةِ، وَمَنْ لاَ يَرَى الإِعَادَةَ عَلَى مَنْ سَهَا فَصَلَّى إِلَى غَيْرِ الْقِبْلَةِ
Sahih al-Bukhari 402b

Narrated Anas:

as above (395).

حَدَّثَنَا ابْنُ أَبِي مَرْيَمَ، قَالَ أَخْبَرَنَا يَحْيَى بْنُ أَيُّوبَ، قَالَ حَدَّثَنِي حُمَيْدٌ، قَالَ سَمِعْتُ أَنَسًا، بِهَذَا‏.‏
Reference : Sahih al-Bukhari 402b
In-book reference : Book 8, Hadith 54
USC-MSA web (English) reference : Vol. 1, Book 8, Hadith 396
  (deprecated numbering scheme)