It was narrated from ‘Abdullah bin ‘Amr that a man asked the Messenger of Allah ﷺ:
“O Messenger of Allah, which (aspect) of Islam is the best?” He said: “Offering food (to the needy) and greeting with Salam those whom you know and those whom you do not know.”

حَدَّثَنَا مُحَمَّدُ بْنُ رُمْحٍ، أَنْبَأَنَا اللَّيْثُ بْنُ سَعْدٍ، عَنْ يَزِيدَ بْنِ أَبِي حَبِيبٍ، عَنْ أَبِي الْخَيْرِ، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، . أَنَّ رَجُلاً، سَأَلَ رَسُولَ اللَّهِ ﷺ فَقَالَ يَا رَسُولَ اللَّهِ أَىُّ الإِسْلاَمِ خَيْرٌ قَالَ " تُطْعِمُ الطَّعَامَ وَتَقْرَأُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ وَمَنْ لَمْ تَعْرِفْ " .