«لو عكسته وبدأت بحرفه الأخير إلى الأول كان الحاصل بعينه هو هذا الكلام»
If the utterance were reversed and read from its last letter to its first, the result would be that very utterance.
This defines qalb. Two similar-sounding words do not suffice: the relevant complete sequence of letters must remain the same when read in reverse order.
Vowel signs, inflectional marks and spaces are not independently counted as letters in the basic test. Normal spelling and word boundaries remain useful for interpreting the meaning, but the defining symmetry is in the letters.