Iklab means to turn into something else or to convert. In tajweed, it means to convert a letter into another letter. Iklab occurs when Tanven (ـًـٍـٌ ) or Noon without harakah (ن ) is followed by Ba (ب ) . In this case, the Noon of Tanven or Noon without harakah is turned into Mem (م ) harfine and pronounced with a ghunna. To do the Iqlab is compulsory in tajweed.
اَنْبَاَهُمْ , مِنْ بَعْدِ , سَمِيعٌ بَصِيرٌ , لَيُنْبَذَنَّ