Riyad as-SalihinChapter 17Hadith 950
Full Sharh — Riyad as-Salihin 950
وعن ابن عباس رضي الله عنهما أن رسول الله صلى الله عليه وسلم قال: "لا يخلون أحدكم بامرأة إلا مع ذي محرم" ((متفق عليه)).
English Translation
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).".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of the Prohibited actions
Hadith Number
950