ENOfficial
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.”
Source: sunnah.com
Other translations
Arabic
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 ـ صلى الله عليه وسلم ـ فَقَالَ يَا رَسُولَ اللَّهِ أَىُّ الإِسْلاَمِ خَيْرٌ قَالَ " تُطْعِمُ الطَّعَامَ وَتَقْرَأُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ وَمَنْ لَمْ تَعْرِفْ " .
sunnah.com