Sahih Al Bukhari 1: Chapter 4, Hadith 135

(135) No Salat (prayer) is accepted without ablution (i.e. to remove, the small Hadath by ablution or the big Hadath by taking a bath)

حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ الْحَنْظَلِيُّ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَخْبَرَنَا عَبْدُ الرَّزَّاقِ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَخْبَرَنَا مَعْمَرٌ، ‏‏‏‏‏‏عَنْ هَمَّامِ بْنِ مُنَبِّهٍ، ‏‏‏‏‏‏أَنَّهُ سَمِعَ أَبَا هُرَيْرَةَ، ‏‏‏‏‏‏يَقُولُ:‏‏‏‏ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ:‏‏‏‏ "لَا تُقْبَلُ صَلَاةُ مَنْ أَحْدَثَ حَتَّى يَتَوَضَّأَ"قَالَ رَجُلٌ مِنْ حَضْرَمَوْتَ:‏‏‏‏ مَا الْحَدَثُ يَا أَبَا هُرَيْرَةَ؟ قَالَ:‏‏‏‏ فُسَاءٌ أَوْ ضُرَاطٌ.

SAHIH HADITH:

Narrated Abu Huraira: Allah's Apostle said, The prayer of a person who does Hadath (passes urine, stool or wind) is not accepted till he performs the ablution. A person from Hadaramout asked Abu Huraira, What is 'Hadath'? Abu Huraira replied, 'Hadath' means the passing of wind.

REFERENCE:

Sahih Al Bukhari 1: Chapter 4, Hadith 135