A woman should not set out on three (days') journey, but in the company of a Mahram.
Sahih Muslim Book 15, Hadith 467
← Previous Hadith I heard Abu Sa'id al-Khudri (Allah be pleased with him) saying: I heard four things from Allah's Messenger (ﷺ) which impressed me and captivated me (and one out of these is this), that he forbade a woman to undertake journey extending over two days but with her husband, or with a Mahram; and he then narrated the rest of the hadith.

Sahih Muslim Book 15, Hadith 466 Next Hadith → A woman should not set out on a journey extending beyond three nights but with a Mahram.

Sahih Muslim Book 15, Hadith 468