Sahih al-Bukhari, Book 18, Hadith 7 (In-Book) ⓘ
Narrated Ibn `Umar: The Prophet said, "A woman should not travel for more than three days except with a Dhi-Mahram (i.e. a male with whom she cannot marry at all, e.g. her brother, father, grandfather, etc.) or her own husband.)"
حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ الْحَنْظَلِيُّ، قَالَ قُلْتُ لأَبِي أُسَامَةَ حَدَّثَكُمْ عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ " لاَ تُسَافِرِ الْمَرْأَةُ ثَلاَثَةَ أَيَّامٍ إِلاَّ مَعَ ذِي مَحْرَمٍ " .
also referenced under: Hadith 1086 (DarusSalam) & Volume 2, Book 20, Hadith 192 (USC-MSA)