التَّخْصِيصُ
Restricting an attribution or excluding an unwanted alternative.
مَا أَنَا قُلْتُ
It was not I who said it.
Ana is placed before qultu, bringing special attention to the alleged speaker. In an appropriate context, the expression denies that the speaker was the one who uttered the statement while leaving open that someone else may have said it.
Exclusivity is not merely a mechanical effect of every fronted word. Context completes the meaning. In response to an accusation directed specifically at oneself, ma ana qultu foregrounds the denial of that attribution.