He caused some harm to his friends; does he have to tell them if he intends to repent?
Question

                I got to know one of the youth who have gone astray, and he used me to make some young people fall into his trap. I helped him in fact, but some of that did not happen, praise be to Allaah. I even helped him to do witchcraft against one young man, but it did not harm him, praise be to Allaah.

 I have repented now, and I keep away from that deviant young man and keep company with good people. I have also started to memorize the Holy Qur’aan.

 My question is: is it one of the conditions of my repentance that I should tell him about the witchcraft I did, in order for my repentance to be accepted?.
Praise be to Allah.
    We praise Allaah for guiding you to repent, and to keep away 
    from these bad friends. You have to keep on thanking Allaah and asking Him 
    to make you steadfast and to guide you. 

    The rights of other people must be restored if the wrong done 
    involved material things. With regard to intangible things, such as gossip, 
    the correct view – and Allaah knows best – is that he does not have to tell 
    him if the person does not know about that, so it is sufficient to pray for 
    forgiveness for his sin, and to pray for forgiveness for his brother too, in 
    return for the harm done by his gossiping and backbiting about him. 

    The harm done to this young man by means of plotting and 
    witchcraft comes under the heading of intangible matters, so you do not have 
    to tell him about what you did; it is sufficient for you to fulfil the 
    conditions of sincere repentance, namely regretting what you did, giving it 
    up, and resolving not to go back to it again, as well as stopping the 
    evildoer and others as much as you can. 

    See also the answer to question no.
    6308. 

    But if that young man or anyone else knows about the plots 
    and tricks you used against him, then you have to apologize to him and ask 
    for his forgiveness, because you are only allowed not to tell him if he did 
    not know so that he will not be upset by that, and lest that lead to cutting 
    off ties and the stirring up of enmity and hatred between you. But if he 
    knows that you did this evil thing, then the reason not to tell him is no 
    longer applicable and your apologizing to him will serve a purpose. 

    We ask Allaah to accept your repentance. And Allaah knows best.