Tafsir by mere opinion is not allowed
Muhammad bin Jarir reported that Ibn ‘Abbas (رضي الله عنه) said that the Prophet (صلى الله عليه وسلم) said,
[Whoever explains the Qur’an with his opinion or with what he has no knowledge of, then let him assume his seat in the Fire.]
At-Tirmidhi, An-Nasa’i and Abu Dawud also recorded this Hadith. At-Tirmidhi said, “Hasan”.
Ibn Jarir (At-Tabari) reported that Abu Ma’mar said that Abu Bakr As-Siddiq (رضي الله عنه) said, ” Which land will carry me and which heaven will shade me if I said aboutAllah’s Book that which I have no knowledge of? ”
Ibn Jarir also recorded that Ibn Abi Mulaykah said that Ibn ‘Abbas (رضي الله عنه) was asked about an Ayah, “That if any of you is asked about, he will indulge in its Tafsir.” without hesitation Ibn ‘Abbas refused to say anything about it (meaning with his opinion). This narration has an authentic chain of narrators.