And indeed, he is to that a witness. (100:7)

Almuntakhab Fi Tafsir Alquran Alkarim

And by his behavior he bears witness to this discord

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(100:7) and he himself is a witness to that, *5

And indeed, he is to that a witness. meaning

*5) That is his own conscience and his own deeds are a witness to it; then there are many disbelievers also who by their own tongue express their ingratitude openly 'for they do not even believe that God exists to say nothing of acknowledging His blessings for which they may have to render gratitude to Him.
 

And indeed, he is to that a witness. meaning in Urdu

اور وہ خود اِس پر گواہ ہے