Tie In Musa عليه السلام Tongue
Eating of ‘Burning coal’ is a historical narration for which we have no authentic basis to prove whether it actually happened or not, and even if happened, what was the exact nature of this incident. The verse however has no need to be seen in the context of this historical narration, it can be understood independently in terms of a derogatory remark to bring someone down e.g. “this person A is not even a good speaker, let alone a philosopher or an intellectual”.
Some people are more elequent in speech than others. No need to bring burning cole incident.. It appears that Musa a.s was not very elequent because in another place in Qur’an he a.s says ” my brother Haroon is more elequent than me وَأَخِى هَٰرُونُ هُوَ أَفْصَحُ مِنِّى لِسَانًا فَأَرْسِلْهُ مَعِىَ رِدْءًا يُصَدِّقُنِىٓ