Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "It is not permissible for a woman who believes in Allah and the Last Day to make a journey of one day and night unless she is accompanied by a Mahram (husband or any other relative to whom she is prohibited to marry)."[Al-Bukhari and Muslim].
App reference: Book 8, Hadith 34
Arabic/English book reference: Book 8, Hadith 989