They alone invent lies who do not believe in the words of God, and they are liars.
105
Tafseer
'Abdullāh Ibn 'Abbās / Muḥammad al-Fīrūzabādī
تفسير : (only they invent falsehood) about allah those (who believe not allah's revelations) i.e. muhammad (pbuh) and the qur'an, (and (only) they are the liars) about allah.
Jalāl al-Dīn al-Maḥallī
تفسير : only those invent falsehood who do not believe in god’s signs, the qur’an, by saying that these are the words of a human, and it is they who are the liars (the emphasis is [effected] by way of repetition; wa-inna, ‘and indeed’, and other [combinations of inna] are [used] in refutation of their saying, ‘you are just a fabricator’ [above, q. 16:101]).