There was a man from the Ansar known as Abu Shuayb who had a servant who was a butcher. He said to him, "Prepare a meal for us so that I may invite the Messenger of Allah ﷺ as one of six."So he invited them, but another man followed along with them.The Messenger of Allah ﷺ said to him, "This man has followed us. Will you permit him to join?"He replied, "Yes."
حدثنا أبو الجواب حدثنا عمار بن رزيق عن الأعمش عن أبي سفيان
كان رجل من الأنصار يقال له أبو شعيب وكان له غلام لحام فقال له اجعل لنا طعاما لعلي أدعو رسول الله ﷺ سادس ستة فدعاهم فاتبعهم رجل فقال له رسول الله ﷺ إن هذا قد اتبعنا أفتأذن له قال نعم
Its isnad is sahih. Abu Jawab is Ahwas bin Jawab, a trustworthy narrator who has a narration in Muslim. Bukhari related the hadith at 3/117, in the chapter on injustices, "If someone gives another person permission." It is found in all the Sahihs.