Sayyiduna Abdullah bin Umar (may Allah be pleased with him) narrates this statement of the Prophet (peace and blessings be upon him): "It is not permissible for any woman to undertake a journey of three days except that there is with her a mahram who is permanently unlawful for her (to marry)."
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 2720
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صحيح أبي داود» (1519).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده حسن