For men, as a minimum, the navel area up to below the knees should be covered during Salat. The more a person can cover themselves the better.

For a woman, if she is offering her Salat in an area where non-mahram are not present, then when offering Salat she can keep her hands, up to her forearms, face and feet up to her ankles uncovered – apart from these areas, all of her body should be covered. If non–mahram men are present in the area, then she should also cover her face during Salat.

If someone doesn’t have proper clothing due to poverty or other reasons, then this isn’t a factor that should stop them from offering Salat – they are permitted to offer Salat in whatever clothing they have.