Is henna mustahabb or Sunnah? Is it haram for an unmarried woman to engrave and decorate it? Is a married woman who applies it for her husband, then goes out with it and is seen by strange men, committing a sin? And what is meant by 'Umar ibn al-Khattab's prohibition of engraving and embellishing?

A woman's use of henna, whether for patterns or other permissible adornments, is Islamically sanctioned; in fact, it may even be considered desirable (mustahabb) for her. This is supported by prophetic hadiths, including: "Dye your hands with henna; one of you leaves off dyeing until her hand becomes like a man's hand," and "If I were a woman, I would change your nails," meaning with henna. Henna is an adornment that must be concealed from non-mahram men, based on the general import of Allah's saying: "And let them not expose their adornment." As for Umar's (may Allah be pleased with him) prohibition of patterns and embellishments, it was narrated by Abdur-Razzaq, and Al-Hafiz Ibn Hajar commented that this does not indicate a general prohibition, but rather permissibility, and that the dislike might be in the state of ihram or due to the presence of temptation (fitna). In summary, mere patterning and embellishment are not forbidden, but they may be disliked by some scholars, provided the woman adheres to Islamic manners.