صحيح ابن خزيمه
Sahih Ibn Khuzaymah
كتاب: الصلاةBook of Prayer
(4) بَابُ فَرْضِ الصَّلَوَاتِ الْخَمْسِChapter 4: On the obligation of the five daily prayers
Hadith Q306
وَالدَّلِيلُ عَلَى أَنْ لَا فَرْضَ مِنَ الصَّلَاةِ إِلَّا الْخَمْسَ، وَأَنَّ كُلَّ مَا سِوَى الْخَمْسِ مِنَ الصَّلَاةِ فَتَطَوُّعٌ لَيْسَ شَيْءٌ مِنْهَا فَرْضٌ إِلَّا الْخَمْسُ فَقَطْ
And the explanation of the evidence that only five prayers are obligatory. All prayers besides these five are voluntary. Except for the five prayers, no other prayer is obligatory.
