The Book of Faith
1/14. Chapter:
Clarifying the superiority of Islam, and what part of it is best
Sahih Muslim
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، ح وَحَدَّثَنَا مُحَمَّدُ بْنُ رُمْحِ بْنِ الْمُهَاجِرِ، أَخْبَرَنَا اللَّيْثُ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ أَبِي الْخَيْرِ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، أَنَّ رَجُلاً، سَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم أَىُّ الإِسْلاَمِ خَيْرٌ قَالَ " تُطْعِمُ الطَّعَامَ وَتَقْرَأُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ وَمَنْ لَمْ تَعْرِفْ " .
It is narrated on the authority of 'Abdullah b. 'Amr that a man asked the Messenger of Allah (may peace and blessings be upon him) which of the merits (is superior) in Islam. He (the Holy Prophet) remarked: That you provide food and extend greetings to one whom you know or do not know.
Reference : Sahih Muslim 39In-book reference : Book 1, Hadith 67USC-MSA web (English) reference : Book 1, Hadith 63