Sahih al-Bukhari Book 67, Hadith 166
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."
Allah's Messenger (ﷺ) said, "Beware of entering upon the ladies." A man from the Ansar said, "Allah's Apostle! What about Al-Hamu the in-laws of the wife (the brothers of her husband or his nephews etc.)?" The Prophet (ﷺ) replied: The in-laws of the wife are death itself.
An Ansari woman came to the Prophet (ﷺ) and he took her aside and said (to her). "By Allah, you (Ansar) are the most beloved people to me."