إِنَّا أَعْطَيْنَاكَ الْكَوْثَرَ فَصَلِّ لِرَبِّكَ وَانْحَرْ
Indeed We have granted you al-Kawthar; so pray to your Lord and sacrifice.
The divine utterance begins in the first person through «إِنَّا», then describes God as «رَبِّكَ» in the third person. The shift presents the giver of the gift through the relationship of Lordship and worship.
It is first person → third person. The noun «Lord» also carries its own significant meaning; treating it as only a technical person-switch would flatten the rhetorical point.