What is the expiation for a woman who adorned herself with makeup and passed by a place where there were strange men, having forgotten that she was appearing before them with makeup on?

A woman who leaves her home is required to wear the hijab in the street until she enters a place where she is safe from the gaze of non-mahram men. If she predominantly believes there are no men at the door and she forgets to cover her face, we hope she will not be held accountable.

However, if she is negligent, she must repent, feel remorse, and resolve not to return to the sin. There is no specific expiation, but she should frequently seek forgiveness and perform good deeds, in accordance with the Almighty's saying: "And those who, when they commit an immorality or wrong themselves, remember Allah and seek forgiveness for their sins – and who can forgive sins except Allah? – and [who] do not knowingly persist in what they have done" (Qur’an 3:135), and His saying: "And establish prayer at the two ends of the day and at the approach of the night. Indeed, good deeds do away with evil deeds. That is a reminder for those who remember" (Qur’an 11:114), and the Prophet's (peace be upon him) saying: "Fear Allah wherever you are, and follow up a bad deed with a good one which will wipe it out."