SHAFAQNA – Woman should conceal her body and hair from a man who is non-Mahram, and as an obligatory precaution, she should conceal herself even from a Na-baligh boy who is able to discern between good and evil, and could probably be sexually excited. But she can leave her face and hands upto wrists uncovered in the presence of Na-Mahram, as long as it does not lead him to casting a sinful, evil glance or her to doing something forbidden; for in both these cases, she must cover them.
Ayatollah Ali Sistemi