All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Many scholars of Tajweed (i.e. the rules of the recitation of the Quran) reported scholarly agreement about making Idghaam (assimilation, i.e. joining two letters together to become one letter) of the letter Qaaf with the letter Kaaf in the Saying of Allaah (ألم نخلقكم من ماء مهين)[Quran 77:20] (which means): {Did We not create you from a liquid disdained?}.
The reason for this Idghaam as stated by Abu Shaamah in his explanation of “Ash-Shaatibiyyah” is that they come out from the same place of articulation (and follow each other) in one word.
Allaah Knows best.