وَأَنَّ عَذَابِى هُوَ ٱلْعَذَابُ ٱلْأَلِيمُ
Wa anna 'azaabee uwal 'azaabul aleem
and that my punishment is the painful punishment.
Both halves of the announcement go to the same hearers, ʿibādī, my servants, and the grammar of 15:49 runs straight on into this line as one sentence broken across two verses. Mercy carries two names in that first half while punishment is named once and doubled by repeating the noun, an imbalance commentators have long read as deliberate: whoever is told of the forgiveness is the one being warned.