I heard Messenger of Allah ﷺ delivering a sermon and making this observation:" No person should be alone with a woman except when there is a Mahram with her, and the woman should not undertake journey except with a Mahram." A person stood up and said: Messenger of Allah, my wife has set out for pilgrimage, whereas I am enlisted to fight in such and such battle, whereupon he said:" You go and perform Hajj with your wife."
سَمِعْتُ النَّبِيَّ ﷺ يَخْطُبُ يَقُولُ لاَ يَخْلُوَنَّ رَجُلٌ بِامْرَأَةٍ إِلاَّ وَمَعَهَا ذُو مَحْرَمٍ وَلاَ تُسَافِرِ الْمَرْأَةُ إِلاَّ مَعَ ذِي مَحْرَمٍ فَقَامَ رَجُلٌ فَقَالَ يَا رَسُولَ اللَّهِ إِنَّ امْرَأَتِي خَرَجَتْ حَاجَّةً وَإِنِّي اكْتُتِبْتُ فِي غَزْوَةِ كَذَا وَكَذَا قَالَ انْطَلِقْ فَحُجَّ مَعَ امْرَأَتِكَ