«وَمَا أُبَرِّئُ نَفْسِي إِنَّ النَّفْسَ لَأَمَّارَةٌ بِالسُّوءِ»
I do not claim that my own soul is blameless; indeed the soul persistently urges toward evil.
The opening clause denies self-exoneration. A question arises: “Why not claim innocence?” The following clause supplies a general explanation about the self and its inclination toward wrongdoing.
«إِنَّ النَّفْسَ لَأَمَّارَةٌ بِالسُّوءِ» has the function of explanation and justification, not simply a new piece of unrelated information. That is why it is analysed within the rhetorical use of separation.