Prohibition of Meeting a non-Mahram Woman in Seclusion

Ibn Abbas (May Allah be pleased with them) said:
The Messenger of Allah ﷺ said, "No one of you should meet a woman in privacy unless she is accompanied by a Mahram (i.e., a relative within the prohibited degrees)."

[Al-Bukhari and Muslim].

وعن ابن عباس رضي الله عنهما أن رسول الله ﷺ قال: "لا يخلون أحدكم بامرأة إلا مع ذي محرم" ((متفق عليه)).

Buraidah (May Allah be pleased with him) said:
The Messenger of Allah ﷺ said, "The sanctity of the wives of Mujahidun (i.e., those who strive hard and fight in the way of Allah) for those who remain at home (i.e., those who do not go to the battlefield to fight Jihad) is like the sanctity of their own mothers. Anyone who remains behind to look after the family of a Mujahid and betrays his trust, will be made to stand on the Day of Resurrection before the Mujahid who will take away from his meritorious deeds whatever he likes till he is satisfied." The Messenger of Allah ﷺ turned toward us and said, "Now, what do you think (i.e., will he leave anything with him)?"

[Muslim].

وعن بريدة رضي الله عنه قال: قال رسول الله ﷺ : "حرمة نساء المجاهدين على القاعدين كحرمة أمهاتهم، ما من رجل من القاعدين يخلف رجلا من المجاهدين في أهله، فيخونه فيهم إلا وقف له يوم القيامة، فيأخذ من حسناته ما شاء حتى يرضى" ثم التفت إلينا رسول الله ﷺ وقال: "ما ظنكم؟" ((رواه مسلم)).