Imaam Barbahaaree (rahimahullaah) said:
‘It is not permitted for a man to say, ‘So and so is a person of the Sunnah’ until he knows that he combines the characteristics of the Sunnah, so it is not said of him, ‘a person of the Sunnah’ until he combines all the Sunnah.’
Shaikh Saaleh Al-Fawzaan (may Allaah preserve him) commented on the above statement of Imaam Barbahaaree (rahimahullaah), saying:
Do not give Taskiyah to a person and praise of him, except from knowledge; lest the people become deceived by your praise of him, whilst he is not what (you have stated about him). So when his real affair and path is clear to you, his knowledge and steadfastness, then you can give him Tazkiyah. As for giving out praise and recommendation whilst not knowing of anything about him, then this is a dangerous Tazkiyah through which the people will be deceived by this person.
Had only those who give commendations to the people stopped at that (i.e. put it in its proper place), then they would not give recommendation, except for one who fulfils the conditions of giving Tazkiyah; because Tazkiyah is a ‘Witness’, so, if the Tazkiyah is not correct it will be a false witness.
And concerning the statement of Imaam Barbahaaree: ‘until he knows that he combines the characteristics of the Sunnah’
Shaikh Saaleh Al-Fawzaan commented on the above statement saying: The characteristics of the Sunnah are to be in Aqeedah, Knowledge and adherence to the Salafus Saaleh. But if there is not in him except a single characteristic of the (Sunnah), then he is not judged to be from Ahlus Sunnah on the basis of a single characteristic or one thing, so what about the one who does not have anything from that?
It’haaful Qaaree Bitta’liqaat Alaa Sharhis Sunnah Lil Imaam Barbahaaree; Vol: 2; Pages: 275-276