Musnad Ahmad 27:75

'Abd al-A'la narrated to us, from Ma'mar, from al-Zuhri, from Salim, from Ibn 'Umar, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If the wife of one of you asks permission to go to the mosque, do not prevent her." He said: The wife of 'Umar ibn al-Khattab used to pray in the mosque. He said to her: "You know that I do not like it." She said: "By Allah, I will not stop until you forbid me." He said: Then 'Umar was stabbed while she was in the mosque.