What is the ruling on a woman who has reached adulthood but does not wear the hijab?

If a girl reaches the age of legal responsibility, she is obligated to wear the hijab (definition), as it is one of the commands of the Sharia (definition) and a symbol of Muslim women, indicating modesty, chastity, and dignity. Allah Almighty commanded it in His saying: {O Prophet, tell your wives and your daughters and the women of the believers to draw over themselves their outer garments. That is more suitable that they will be known and not be abused.} [Al-Ahzab: 59], to distinguish them from slave women and protect them from harm, and for their appearance to indicate their piety and faith. Allah Almighty also mandated the hijab for the Mothers of the Believers with His saying: {And when you ask [his wives] for something, ask them from behind a partition. That is purer for your hearts and their hearts.} [Al-Ahzab: 53]. This obligation includes all women of the Ummah, as the entire woman is 'awrah (private, to be covered), and the obligation of the hijab is even more stringent today, especially in an era where corruption and immorality have become widespread.