Should a man equally divide his time among his menstruating and postpartum wives?

The fundamental principle is the obligation to divide time equally among wives. However, it has become customary in many lands that a woman in postpartum bleeding (nifas (definition)) is not entitled to an equal division of time (qasm); this is because she stays with her mother or her mother comes to live with her to serve her, and she is content with waiving her right to qasm. Sheikh Abd al-Rahman al-Sa'di was asked about this and replied: "The well-known opinion in the madhhab (definition) is that qasm is obligatory for both. However, the correct view, upon which practice is based, is that a menstruating woman is entitled to qasm, but a woman in postpartum bleeding is not entitled to qasm, due to the prevailing custom in this regard and her contentment with waiving qasm."