'Abdullah ibn 'Amr reported that a man said, "Messenger of Allah, which aspect of Islam is best?" He replied, "Feeding people and greeting those you know and those you do not know."  

أَنَّ رَجُلاً قَالَ يَا رَسُولَ اللهِ أَيُّ الإِسْلاَمِ خَيْرٌ؟ قَالَ تُطْعِمُ الطَّعَامَ وَتُقْرِئُ السَّلاَمَ عَلَى مَنْ عَرَفْتَ وَمَنْ لَمْ تَعْرِفْ