Is it obligatory for me to testify in a stabbing incident, knowing that the victim is a bad person and known for his ill-manners, and the stabbing occurred because he stole a shoe?

Allah Almighty says: (O you who have believed, be persistently Qawwameen for Allah, witnesses in justice, and do not let the hatred of a people prevent you from being just. Be just; that is nearer to righteousness. And fear Allah; indeed, Allah is Acquainted with what you do), and He says: (And do not conceal testimony), and He says: (And establish testimony for Allah). Al-Shafi'i preserved from the people of knowledge that these verses mean that the witness must bear witness against his parents and his child, and against relatives and strangers, and against the hated one, whether close or far. He should not conceal it from anyone, nor favor anyone with it, nor withhold it from anyone. If bearing witness becomes a personal obligation such that no one else can sufficiently bear it, then he is obliged to do so, unless he is unable to bear it or it harms him. The immorality of the person testified for does not prevent the bearing of testimony.