Sahih al-Bukhari 2456
Narrated Abu Mas`ud:
There was an Ansari man called Abu Shu'aib who had a slave butcher. Abu Shu'aib said to him, 
"Prepare a meal sufficient for five persons so that I might invite the Prophet (ﷺ) besides other four 
persons." Abu Shu'aib had seen the signs of hunger on the face of the Prophet (ﷺ) and so he invited him. 
Another man who was not invited, followed the Prophet. The Prophet (ﷺ) said to Abu Shu'aib, "This man 
has followed us. Do you allow him to share the meal?" Abu Shu'aib said, "Yes."
حَدَّثَنَا أَبُو النُّعْمَانِ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنِ الأَعْمَشِ، عَنْ أَبِي وَائِلٍ، عَنْ أَبِي مَسْعُودٍ، أَنَّ رَجُلاً، مِنَ الأَنْصَارِ يُقَالُ لَهُ أَبُو شُعَيْبٍ كَانَ لَهُ غُلاَمٌ لَحَّامٌ فَقَالَ لَهُ أَبُو شُعَيْبٍ اصْنَعْ لِي طَعَامَ خَمْسَةٍ لَعَلِّي أَدْعُو النَّبِيَّ صلى الله عليه وسلم خَامِسَ خَمْسَةٍ‏.‏ وَأَبْصَرَ فِي وَجْهِ النَّبِيِّ صلى الله عليه وسلم الْجُوعَ ـ فَدَعَاهُ، فَتَبِعَهُمْ رَجُلٌ لَمْ يُدْعَ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏
"‏ إِنَّ هَذَا قَدِ اتَّبَعَنَا أَتَأْذَنُ لَهُ ‏"‏‏.‏ قَالَ نَعَمْ‏.‏