'Bring me blocks of iron, until when he had leveled [the space] between the two mountain walls,' meaning the tops of the two mountains, according to the tafsir of Mujahid, i.e., he blocked what was between them. 'He said, "Blow,"' meaning upon the iron. 'Until when he made it [like] fire,' meaning he heated it with fire. 'He said, "Bring me,"' meaning give me, '"that I may pour over it molten copper."' There is an inversion here: 'Give me molten copper, that I may pour it over it.' The 'qitr' is copper. Thus, he made iron its foundation, and he made copper its mortar.

Muhammad [Ibn Abi Zamanin] says: The 'milat' (mortar) is the clay that is placed in construction between every two rows.