Is it permissible for a man to have sexual intercourse with his four wives one after another if they are all consenting?

It is not permissible for a Muslim man to have intercourse with one of his wives in the presence of another. This goes against the principles of privacy, modesty, and virtuous morals. Scholars have explicitly forbidden intercourse in the presence of anyone, whether awake or asleep. Ibn Umar even went so far as to instruct the removal of everyone from the house, even an infant in the cradle. Scholars also disliked merely hearing the sounds [of intercourse].

However, if they are in separate rooms that block sight and sound, there is no objection to having intercourse with one after another directly. It is recommended for him, if he has not performed ghusl (ritual bath), to wash his private parts and perform wudu' (ablution) before engaging with the other wife.