كتاب الإيمان
1
The Book of Faith
(19)
Chapter: Encouragement to honor one's neighbor and guest, and the obligation to remain silent unless one has something good to say, and the fact that all of that is part of faith
(19)
باب الْحَثِّ عَلَى إِكْرَامِ الْجَارِ وَالضَّيْفِ وَلُزُومِ الصَّمْتِ إِلاَّ مِنَ الْخَيْرِ وَكَوْنِ ذَلِكَ كُلِّهِ مِنَ الإِيمَانِ

It is reported on the authority of Abu Huraira that the Messenger of Allah (ﷺ) observed:

He who believes in Allah and the Last Day should either utter good words or better keep silence; and he who believes in Allah and the Last Day should treat his neighbour with kindness and he who believes in Allah and the Last Day should show hospitality to his guest.
حَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَنْبَأَنَا ابْنُ وَهْبٍ، قَالَ أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيَقُلْ خَيْرًا أَوْ لِيَصْمُتْ وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيُكْرِمْ جَارَهُ وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيُكْرِمْ ضَيْفَهُ ‏"‏ ‏.‏
Reference : Sahih Muslim 47 a
In-book reference : Book 1, Hadith 80
USC-MSA web (English) reference : Book 1, Hadith 75
  (deprecated numbering scheme)