As-Saduq on absolute equality in a polygamous partnership

Muhammad Ibn Ali As-Saduq writes:

وَلَا بَـأسَ إِذَا كَـانَ لِـلـرَّجُـلِ امْـرَأَتَـانِ أَنْ يُـفَـضِّـلَ إِحْـدَاهُـمَـا عَـلَـى الْأُخْـرَى

“There is no problem if someone happens to have two wives and he prefers one of them over the other.” [Al-Muqni’, page 319]