«تَعْلَمُ مَا فِي نَفْسِي وَلَا أَعْلَمُ مَا فِي نَفْسِكَ»
“You know what is within me, while I do not know what is with You.”
The first use of nafsī refers to the speaker’s inner state. The second use nafsika is understood with regard to the appropriate meaning in its divine attribution, not as human psychology.
The rhetorical explanation observes a relationship of wording between the two clauses while maintaining the distinction between their intended senses.