فِي عِبَادِي

فِي عِبَادِي is a phrase (شِبْهُ الجُمْلَةِ) consisting of a preposition followed by a possessive nominal compound

PhraseParticle/Noun/NounNounNounParticle
شِبْهُ الجُمْلَةِ جَارٌ وَمَجْرُوْرٌ وَهُوَ مُضَافٌ وَ مُضَافٌ إِلَيْهِمُضَافٌ إِلَيْهِاسْمٌ مَجْرُوْرٌ وَهُوَ مَضَافٌحَرْفُ جَرٍّ
PhraseCompoundPossessive NounGenitive noun/Noun possessedParticle of pulling down
  
among my slavesفِي عِبَادِي=ي+عِبَادِ+فِي
 among the slaves of mineminethe slaves ofin/among
Surah/Below is the only verse in the holy Quran containing the compoundفِي عِبَادِي
Verse
89-29Enter among My slavesفَادْخُلِى فِي عِبَادِى