It was narrated from Safiyyah bint Shaybah that ‘Aa’ishah (may Allaah be pleased with her) used to say: When these words were revealed – “and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms)” – they took their izaars (a kind of garment) and tore them from the edges and covered their faces with them.
Narrated by al-Bukhaari, 4481. The following version was narrated by Abu Dawood (4102)
Edit: Ibn Hajar said in Fath al-Baari: There is a report of Ibn Abi Haatim via ‘Abd-Allaah ibn ‘Uthmaan ibn Khaytham from Safiyyah that explains that. This report says: We mentioned the women of Quraysh and their virtues in the presence of ‘Aa’ishah and she said: “The women of Quraysh are good, but by Allaah I have never seen any better than the women of the Ansaar, or any who believed the Book of Allaah more strongly or had more faith in the Revelation. When Soorat al-Noor was revealed – “and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms)” – their menfolk came to them and recited to them what had been revealed, and there was not one woman among them who did not go to her apron, and the following morning they prayed wrapped up as if there were crows on their heads. It was also narrated clearly in the report of al-Bukhaari narrated above, where we see ‘Aa’ishah (may Allaah be pleased with her), who was so knowledgeable and pious, praising them in this manner and stating that she had never seen any women who believed the Book of Allaah more strongly or had more faith in the Revelation. This clearly indicates that they understood from this verse – “and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms)” – that it was obligatory to cover their faces and that this stemmed from their belief in the Book of Allaah and their faith in the Revelation. It also indicates that women’s observing hijab in front of men and covering their faces is an act of belief in the Book of Allaah and faith in the Revelation. It is very strange indeed that some of those who claim to have knowledge say that there is nothing in the Qur’aan or Sunnah that says that women have to cover their faces in front of non-mahram men, even though the Sahaabi women did that in obedience to the command of Allaah in His Book, out of faith in the Revelation, and that this meaning is also firmly entrenched in the Sunnah, as in the report from al-Bukhaari quoted above. This is among the strongest evidence that all Muslim women are obliged to observe hijab.