Does the use of a condom permit intercourse during lochia (postpartum bleeding), and if it is not permissible, is expiation obligatory if one was ignorant of the ruling?

It is forbidden to have intercourse with a woman in postpartum bleeding (nifas) during the flow of blood or after its cessation and before ghusl (ritual bath). A condom does not make this forbidden intercourse permissible. However, if the couple were ignorant of the prohibition, there is no sin upon them and no expiation, for nifas resembles menstruation (hayd) in most rulings.