he means that he stayed up all night until the daughters of the coffin turned and they turn over at the end of the night. and the daughters of the coffin were shaken because they set. that is why they make guidance by them and by the two stars. alrai said
يريد أنه سهر ليلته كلها الى أن دارت بنات نعش، وهى تنقلب فى آخر الليل. وخض بنات نعش لأنها تغيب. ولذلك يجعلون الاهتداء بها وبالفرقدين قال الراعى