Sunan Ibn Majah
615
Very Daif+3

It was narrated that 'Abdullah bin Mas'ud said:"The Messenger of Allah said: 'No one of you should bathe in open land or on a roof where he is not concealed; even if he does not see anyone, he can still be seen

Very DaifAl-Albani
Very DaifMuhammad Fouad Abd al-Baqi