Al-Adab Al-Mufrad #1104
The People of the Book
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
حَدَّثَنَا يَحْيَى بْنُ بِشْرٍ، قَالَ: حَدَّثَنَا الْحَكَمُ بْنُ الْمُبَارَكِ، قَالَ: حَدَّثَنَا عَبَّادٌ يَعْنِي ابْنَ عَبَّادٍ، عَنْ عَاصِمٍ الأَحْوَلِ، عَنْ أَبِي عُثْمَانَ النَّهْدِيِّ قَالَ: كَتَبَ أَبُو مُوسَى إِلَى رُهْبَانٍ يُسَلِّمُ عَلَيْهِ فِي كِتَابِهِ، فَقِيلَ لَهُ: أَتُسَلِّمُ عَلَيْهِ وَهُوَ كَافِرٌ؟ قَالَ: إِنَّهُ كَتَبَ إِلَيَّ فَسَلَّمَ عَلَيَّ، فَرَدَدْتُ عَلَيْهِ.
Abu 'Uthman an-Nahdi said, "Abu Musa wrote to a Persian grandee
and greeted him in his letter. He was asked, 'Do you greet him when he
is an unbeliever?' He replied, 'He wrote to me and greeted me, so I have
answered him.'"
About Al-Adab Al-Mufrad
This hadith is #1104 from Al-Adab Al-Mufrad, in the Book of The People of the Book.