'Abdu'r-Rahman said, "Ibn 'Umar passed by a Christian who greeted him and Ibn 'Umar returned the greeting He was told that the man was a Christian. When he learned that, he went back to him and said, 'Give me back my greeting.'"
حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ، قَالَ: أَخْبَرَنَا سُفْيَانُ، عَنْ أَبِي جَعْفَرٍ الْفَرَّاءِ، عَنْ عَبْدِ الرَّحْمَنِ قَالَ: مَرَّ ابْنُ عُمَرَ بِنَصْرَانيٍّ فَسَلَّمَ عَلَيْهِ، فَرَدَّ عَلَيْهِ، فَأُخْبِرَ أَنَّهُ نَصْرَانِيٌّ، فَلَمَّا عَلِمَ رَجَعَ إِلَيْهِ فَقَالَ: رُدَّ عَلَيَّ سَلامِي.

Grade: Hasan (Al-Albani) حـسـن (الألباني) حكم:
Reference : Al-Adab Al-Mufrad 1115
In-book reference : Book 44, Hadith 15