From Sahih Muslim (Hadith 3264):
Qaza'ah reported: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
Reference: Muslim 3264