Question:

Is it permissible to touch the books of Tafsir without wudhu?

Answer:

It is permissible to touch the books of Tafsir without wudhu because they are considered commentary and the verses that are in them are less than the commentary. The Nabi writing letters to the kuffar in which there were verses can be used as evidence for this issue. This indicates that the ruling is for the majority and overwhelming (portion).

If the commentary and the verses are equal then based on the rule that is famous to the people of knowledge i.e. “When an evidence of permissibility and one of prohibition come together and none of the two is singled out by a reason of preference, then the aspect of prohibition is given preference”, if the Quran and Tafsir (commentary) are equal it would be given the ruling of the Quran. And if the Tafsir is more, even by a little, it would be given the ruling of Tafsir.

Shaikh Muhammad Ibnul Uthaimeen
Majmooah Fatawa Wa Rasaail Ibnul Uthaimeen Vol.11 Pg.214-215
 
Touching the Quran without Wudhu
In a previous fatwa Shaikh Ibn Uthaimeen said:

“It is not permissible for anyone to touch the Quran unless he is clean and with wudhu.”

Majmooah Fatawa Wa Rasaail Ibnul Uthaimeen Vol.11 Pg.213