And a shadow from Yahmum,
the shadow of smoke, according to Ibn Abbas, Mujahid, Ikrimah, Abu Salih, Qatadah, As-Suddi and others.
In a similar statement, Allah said,
انطَلِقُواْ إِلَى مَا كُنتُمْ بِهِ تُكَذِّبُونَ انطَلِقُواْ إِلَى ظِلٍّ ذِى ثَلَـثِ شُعَبٍ لاَّ ظَلِيلٍ وَلَا يُغْنِى مِنَ اللَّهَبِ إِنَّهَا تَرْمِى بِشَرَرٍ كَالْقَصْرِ كَأَنَّهُ جِمَـلَةٌ صُفْرٌ
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وَيْلٌ يَوْمَيِذٍ لِّلْمُكَذِّبِينَ
"Depart you to that which you used to deny! Depart you to a shadow in three columns, neither shady nor of any use against the fierce flame of the Fire." Verily, it throws sparks like fortresses, as if they were yellow camels or bundles of ropes. Woe that Day to the deniers. (77;29-34).
Allah said in this Ayah,
وَظِلٍّ مِّن يَحْمُومٍ
(And a shadow from Yahmum), meaning, black smoke,
لاَّا بَارِدٍ وَلَا كَرِيمٍ