Musnad Ahmad Hadith 4333

‘Umar bin al-Khattab (رضي الله عنه) surpassed the people in four matters with regard to the issue of the captives on the day of Badr, when he said that they should be executed, and Allah revealed the words, "Were it not a previous ordainment from Allah, a severe torment would have touched you for what you took” (al-Anfal 8:68); with regard to hijab, when he told the wives of the Prophet (ﷺ) to observe hijab and Zainab said to him, Do you want to tell us what to do, O son of al-Khattab, when Revelation comes down in our houses? Then Allah revealed the words, "And when you ask (his wives) for anything you want, ask them from behind a screen" (al-Ahzab 33:53), when the Prophet (ﷺ) prayed for him by saying, "O Allah, support Islam with ‘Umarʼʼ; and when he nominated Abu Bakr (as caliph) and was the first one to swear allegiance to him.