Knowledge of Arabic Is Not Sufficient to do Tafsir of Quran
One of the greatest Hadith masters and Faqih, Imam Nawawi ra said:
"It is not sufficient to simply know Arabic. Rather, one must also know all that qualified scholars of Tafsir have said about [a given passage of the Quran], for they may have consensus that the apparent [meaning of a verse, for example,] is something to be disregarded and that what is intended is a specific or implied meaning, or something else contrary to the obvious. Likewise, if a phrase has different meanings and it is known that one of those meanings is intended, one then explicates each occurrence [of the phrase] that comes [separately].
All of the foregoing [depicts] the offering of Tafsir by way of [uninformed] opinion, and this is unlawful.
And God knows best."
Source: Etiquette With the Quran, p99.