[Abu Dawud and At-Tirmidhi].
And in a version narrated by Abu Dawud "He should not sit between two men without their permission."
وفى رواية لأبى داود: "لا يجلس بين رجلين إلا بإذنهما".
Reference | : Riyad as-Salihin 828 |
In-book reference | : Book 4, Hadith 16 |