That you provide food and extend greetings to one whom you know or do not know.  

أَنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ ﷺ أَىُّ الإِسْلاَمِ خَيْرٌ قَالَ تُطْعِمُ الطَّعَامَ وَتَقْرَأُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ وَمَنْ لَمْ تَعْرِفْ  

Verily a person asked the Messenger of Allah (may peace and blessings be upon him) who amongst the Muslims was better. Upon this (the Holy Prophet) remarked: From whose hand and tongue the Muslims are safe.  

أَنَّهُ سَمِعَ عَبْدَ اللَّهِ بْنَ عَمْرِو بْنِ الْعَاصِ يَقُولُ إِنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ ﷺ أَىُّ الْمُسْلِمِينَ خَيْرٌ قَالَ مَنْ سَلِمَ الْمُسْلِمُونَ مِنْ لِسَانِهِ وَيَدِهِ  

A Muslim is he from whose hand and tongue the Muslims are safe.  

سَمِعْتُ النَّبِيَّ ﷺ يَقُولُ الْمُسْلِمُ مَنْ سَلِمَ الْمُسْلِمُونَ مِنْ لِسَانِهِ وَيَدِهِ  

I asked the Messenger of Allah which (attribute) of Islam is more excellent. Upon this he remarked: One in which the Muslims are safe, protected from the tongue and hand of (other Muslims).  

قُلْتُ يَا رَسُولَ اللَّهِ أَىُّ الإِسْلاَمِ أَفْضَلُ قَالَ مَنْ سَلِمَ الْمُسْلِمُونَ مِنْ لِسَانِهِ وَيَدِهِ  

Ibrahim b. Sa'id al-Jauhari has narrated this hadith with the same words in addition to these. The Messenger of Allah (may peace and blessings be upon him) was asked as to who amongst the Muslims is better, and the rest of the hadith was narrated like this.  

سُئِلَ رَسُولُ اللَّهِ ﷺ أَىُّ الْمُسْلِمِينَ أَفْضَلُ فَذَكَرَ مِثْلَهُ