(111) باب لاَ يَخْلُوَنَّ رَجُلٌ بِامْرَأَةٍ إِلاَّ ذُو مَحْرَمٍ، وَالدُّخُولُ عَلَى الْمُغِيبَةِ
Narrated Ibn `Abbas:
The Prophet (ﷺ) said, "No man should stay with a lady in seclusion except in the presence of a Dhu- Muhram." A man stood up and said, "O Allah's Messenger (ﷺ)! My wife has gone out intending to perform the Hajj and I have been enrolled (in the army) for such-and-such campaign." The Prophet (ﷺ) said, "Return and perform the Hajj with your wife."
Reference: Sahih al-Bukhari 5233
In-book reference: Book 67, Hadith 166
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 62, Hadith 160