وعن ابن عباس رضي الله عنهما
أن رسول الله صلى الله عليه وسلم قال: «لا يخلون أحدكم بامرأة إلا مع ذي محرم»
The Messenger of Allah (sallallahu alayhi wa sallam) 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).”.
Riyad as-Salihin 1629, Book 18, The Book of the Prohibited actions, Hadith 119. 1 min read