What is the ruling if the father has sexual intercourse with his son's resulting child (the concubine) after the son's act?

Primary text

If the father has sexual intercourse with the concubine after the son's act, he has committed a prohibited act (muharram), but no legal punishment (hadd) is incumbent upon him because the intercourse occurred with property that was already his possession. She then becomes an 'Umm Walad' to the father because he impregnated his owned slave, resembling the case where one has intercourse with his mortgaged slave girl.