The six books
The two Sahihs, whose compilers admitted only what they judged authentic, and the four Sunan, arranged by the chapters of fiqh, where each hadith carries its grade.
صحيح البخاريSahih al-BukhariImam Muhammad ibn Ismaʿil al-Bukhari · d. 256 AH / 870 CE7,552 hadith in 97 books
صحيح مسلمSahih MuslimImam Muslim ibn al-Hajjaj an-Naysaburi · d. 261 AH / 875 CE7,458 hadith in 57 books
سُنَن أبي داودSunan Abī DāwūdAbū Dāwūd as-Sijistānī · d. 275 AH / 889 CE5,274 hadith in 43 books
جامع الترمذيJāmiʿ at-TirmidhīAbū ʿĪsā at-Tirmidhī · d. 279 AH / 892 CE3,998 hadith in 56 books
سُنَن النسائيSunan an-Nasā'īAḥmad an-Nasā'ī · d. 303 AH / 915 CE5,765 hadith in 52 books
سُنَن ابن ماجهSunan Ibn MājahMuḥammad ibn Mājah al-Qazwīnī · d. 273 AH / 887 CE4,343 hadith in 45 books