We are most knowing of what they say when the best of (20:104)

Almuntakhab Fi Tafsir Alquran Alkarim

We know best what they discourse, but those among them with veracious insight will say: You sojourned no more than one day

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

(20:104) We know full well *81 what they will be talking; (We also know that) at that time the most careful estimator among them will say, "No, your life on the Earth was but for a day.' *82

We are most knowing of what they say when the best of meaning

*81) This is a parenthisis that has been inserted to remove this doubt of the hearers: "How has it been known today what the people will be talking in whispers in the Plain of Resurrection?"
*82) This is another parenthisis which has been inserted in answer to another objection raised by some hearer. It appears that when this Surah was being recited, some one might have raised this question as a ridicule: 'Where will these high mountains go on the Day of Resurrection, for it appears from your description of Resurrection that all the people of the world will be running about in a level plain?' In order to understand the background of the question, it should be kept in mind that Makkah, where this Surah was first recited on the occasion of its revelation, is surrounded on all sides by high mountains. The answer to this question follows immediately: "Allah will reduce them to fine dust and scatter it away. "
 

We are most knowing of what they say when the best of meaning in Urdu

ہمیں خوب معلوم ہے کہ وہ کیا باتیں کر رہے ہوں گے (ہم یہ بھی جانتے ہیں کہ) اُس وقت ان میں سے جو زیادہ سے زیادہ محتاط اندازہ لگانے والا ہوگا وہ کہے گا کہ نہیں، تمہاری دنیا کی زندگی بس ایک دن کی تھی