Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that the Prophet Muhammad (peace and blessings be upon him) said: "No woman should undertake a journey of three days or more except that she is accompanied by her father, or her son, or her brother, or her husband, or a close male relative (mahram)."
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2719
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - انظر ما قبله.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرطهما