on the day when the earth and the mountains will quake and the mountains will be like heaps of shifting sand mahīl derives from hāla yahīlu; it is actually mahyūl but the damma sound is considered too heavy for the yā’ and is therefore transposed onto the hā’ while the wāw the second of two unvocalised consonants is omitted on account of it being extra and the damma is replaced by a kasra because of its phonetic affinity the letter yā’.
