Sunan Ibn Majah, Book 24, Hadith 2890 (In-Book) ⓘ
It was narrated that Abu ‘Uqbah, who was the freed slave of some Persian people, said: “I was present with the Prophet on the Day of Uhud. I struck a man from among the idolaters and said: ‘Take that! And I am a Persian slave!’ News of that reached the Prophet and he said: ‘Why did you not say: “Take that! And I am an Ansari slave!?”
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا حُسَيْنُ بْنُ مُحَمَّدٍ، حَدَّثَنَا جَرِيرُ بْنُ حَازِمٍ، عَنْ مُحَمَّدِ بْنِ إِسْحَاقَ، عَنْ دَاوُدَ بْنِ الْحُصَيْنِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي عُقْبَةَ، عَنْ أَبِي عُقْبَةَ، - وَكَانَ مَوْلًى لأَهْلِ فَارِسَ - قَالَ شَهِدْتُ مَعَ النَّبِيِّ صلى الله عليه وسلم يَوْمَ أُحُدٍ فَضَرَبْتُ رَجُلاً مِنَ الْمُشْرِكِينَ فَقُلْتُ خُذْهَا مِنِّي وَأَنَا الْغُلاَمُ الْفَارِسِيُّ . فَبَلَغَتِ النَّبِيَّ صلى الله عليه وسلم فَقَالَ " أَلاَ قُلْتَ خُذْهَا مِنِّي وَأَنَا الْغُلاَمُ الأَنْصَارِيُّ " .
also referenced under: Hadith 2784 (Reference) & Volume 4, Book 24, Hadith 2784 (DarusSalam)