To begin with, giving testimony is a communal obligation that can also be an individual obligation in two situations: when a person is summoned to testify or when the rights of others will be jeopardized if he does not testify. Second, Allah has commanded that in all situations and in the interests of all people, justice be established and witness be given on the basis of fairness. If you would testify in favor of a friend, then testify against him; if you would testify against an adversary, then testify in his favor, even if he is a heretic or an innovator, for it is essential to be just to him. It is not acceptable to be unjust to everyone.