With regards to a person talking about ahaadeeth, the Shaykh Saalih al Fawzaan hafidhahullaah mentions about the hadeeth “The religion is an-Naseehah (sincerity and sincere advice) :
And likewise it is from acting sincerely to the Messenger of Allaah sall Allaahu ‘alaihi wa sallam that you do not enter into declaring ahaadeeth to be authentic or weak when you do not have the ability to do that. So no one goes into this except the people of (that) field and the people who are specialised, from those who are firmly grounded in knowledge and narrations.
As for that reckless attitude towards ahaadeeth which has become manifest among many of the younger people, their authenticating and their criticising them (the ahaadeeth), without having knowledge and without having studied and gained experience beforehand, and without acquiring knowledge from the scholars, then this is something extremely dangerous and is insolent behaviour towards the Sunnah of the Messenger sall Allaahu ‘alaihi wa sallam.
And it is not from acting sincerely towards the Messenger of Allaah that the ignorant people meddle (in these) and call themselves “muhaddithoon” based on (just) being acquainted with one of the books of hadeeth or having memorised a number of them. This is because merely memorising ahaadeeth does not make them muhaddithoon. Rather the muhaddith is only one who is has specialised in the knowledge of narrations; and this is a tremendous field of knowledge that is taken from the scholars and from the people of knowledge and experience.
And it is not for every single person to peruse the books of hadeeth and then declare (ahaadeeth) to be authentic or weak or to explain and expound on them from his own (mind) without having a correct understanding – because this is from acting deceptively towards the Sunnah of the Messenger sall Allaahu ‘alaihi wa sallam. And it is obligatory to act respectfully towards the Sunnah, and for no one to enter into (discussing) it except for one who is specialised in this knowledge.
((Al minhat ul rabbaaniyah page 115-6 of Shaykh Saalih al Fawzaan hafidhahullaah, translated by Nasser ibn Najam)
 Reported by Muslim (55) and by al Bukhaaree in mu’allaq form.