Musnad Ahmad 31:525

Waki’ and Abu Mu’awiyah narrated to us, they said: Al-A’mash narrated to us, from Abu Salih, from Abu Sa’id. And ‘Abd al-Rahman narrated to us, Sufyan narrated to us, from Al-A’mash, from Dhakwan, from Abu Sa’id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "A woman shall not travel a journey of three days or more, except with her father, or her brother, or her son, or her husband, or with a Mahram."