Shaikh Rabee Bin Haadi (hafidha-hullaah) was asked:
A lot of mistakes and differing occurs amongst the Salafi youth as a result of the return or claimed return of an opposer of the Salafi Manhaj to the domain of Salafiyyah; What is your advice to the youth, (as) some of them accept the repentance of (such a person) and others do not.
Whatever the case may be, if a person falls into Sin, doubts and Bidah, but then he repents and turn to Allah in obedience, it is not permissible for anyone to close the door of repentance in his face. That is because the door of repentance is open up until the sun rises from the West. If a person repents and returns (to correctness) it is obligatory to praise and encourage him.
However, some people are well known for lying and inconsistency, so he acts as if he is repentant. So regarding this person, we say: Inshaa-Allaah your repentance is accepted, but we are cautious of him until he manifests his correct repentance.
Abul Hasan Al-Ash-ari announced his repentance on the Mimbar. He used to be an extreme Mutazili-a leader among the leaders of the Mutazilah and he persisted in defence of this evil school of thought for forty years and repented after that. He announced his repentance and from the proofs of his repentance is that he began to author astounding refutations against the Mutizalah-refutation against their doubts. So there are signs of the truthful acts of repentance which dispels the doubts (about his repentance); Meaning: He publicized and manifested to the people that he follows the truth.
So there are affairs that show the truthfulness of (the repentant one) and there are factual evidences that show the untruthfulness of (the one who merely claims to have repented). He (the person) is encouraged if there are factual evidences showing his truthfulness, and (on the other hand) it is incumbent upon the Salafiyyoon to be cautious of him if there are factual evidences showing only the mere claims of his (repentance), as it can be that he is being deceitful.
The groups are widespread; It is not possible to ruin the Salafi youth and hinder the Salafi youth from the Salafi Methodology, except with either claims of (ascription) to Salafiyyah or (claims) of withdrawal from mistakes that are in opposition to the Salafi Manhaj. So if they incline towards him (i.e. the one who claims repentance), he may be able to entice the one he can entice towards a corrupt Methodology. This does take place.
Whatever the case may be, encouragement is given to the one from whom repentance is manifested and it is obligatory to be cautious of the one from whom playing games is manifested. The Salafiyyoon should be alert with regards to the likes of these (people).
[Source: Siyaanatus Salafi Min Waswasati Wa-Talbeesaat Ali Al-Halabi: page: 79-80]