To protect one's tongue
حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا لَيْثٌ، حَدَّثَنَا سَعِيدٌ الْمَقْبُرِيُّ، عَنْ أَبِي شُرَيْحٍ الْخُزَاعِيِّ، قَالَ سَمِعَ أُذُنَاىَ، وَوَعَاهُ، قَلْبِي النَّبِيَّ صلى الله عليه وسلم يَقُولُ " الضِّيَافَةُ ثَلاَثَةُ أَيَّامٍ جَائِزَتُهُ ". قِيلَ مَا جَائِزَتُهُ قَالَ " يَوْمٌ وَلَيْلَةٌ، وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيُكْرِمْ ضَيْفَهُ، وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيَقُلْ خَيْرًا، أَوْ لِيَسْكُتْ ".
Narrated Abu Shuraih Al-Khuza`i: My ears heard and my heart grasped (the statement which) the Prophet (ﷺ) said, "The period for keeping one's guest is three days (and don't forget) his reward." It was asked, "What is his reward?" He said, "In the first night and the day he should be given a high class quality of meals; and whoever believes in Allah and the Last Day, should entertain his guest generously; and whoever believes in Allah and the Last Day should talk what is good (sense) or keep quiet."