Praise be to Allaah.
Among the ahaadeeth which are attributed to the Prophet (peace and blessings of Allaah be upon him), there are some which are saheeh (sound), concerning which there is no doubt that they are the words of the Prophet (peace and blessings of Allaah be upon him). There are others which are da’eef (weak) and there are doubts that they can be attributed to him. Both saheeh and da’eef are well known to the scholars. Books of saheeh have been compiled which include saheeh ahaadeeth such as Saheeh al-Bukhaari and Saheeh Muslim; there are other books which include saheeh ahaadeeth and others, like the other books of hadeeth, The scholars have gone to great lengths to distinguish the saheeh from others, as is well known to young students let alone those who have specialized in the study of the Sunnah.