Is retribution to be carried out publicly before the same number of people who witnessed the incident, or is it permissible for retribution to be carried out in private or before others?

If a man strikes another and enables him to take retribution, then it is permissible for the one who was struck to strike him back in retribution, even though forgiveness is more virtuous. It is not a condition that this occur in the presence of people, for the intention is retribution, and its occurrence has been established from the Companions in the case of a slap and strikes with a whip. Malik and the majority of jurists are of the opinion that there is no retribution for a slap unless it causes an injury, due to the difficulty of achieving equivalence.