Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "It is not lawful for a Muslim woman to travel a journey of one night unless a man who is a mahram of hers is with her."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10140