We know what the earth diminishes of them, and with Us is (50:4)

Almuntakhab Fi Tafsir Alquran Alkarim

But We Have already and thus early known to what extent has the earth consumed of the corpses of their dead, (or it may be; what the earth shall regularly consume of them by death) We keep a book where everything is related in writing and set down in a permanent form

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

(50:4) (Thus do they imagine, although) We know well what the earth takes away from them. With Us is a Record that preserves everything. *4

We know what the earth diminishes of them, and with Us is meaning

*4) That is, "If it cannot be comprehended by intellect, it is their own narrow mind to blame. It does not mean that Allah's knowledge and power also should be narrow. They think that it is in no way possible to collect the scattered particles of the bodies of the countless human beings who have died since the beginning of creation and will die till Resurrection. But the fact is that Allah directly knows each of those particles in whatever form and in whichever place they are. Furthermore, a full record of this is being maintained in the Register of Allah, which has not left out any particle un-recorded. Then, as soon as AIIah commands, His angels will forthwith take out every particle from wherever it is with the help of this record, and will make up the same bodies once again in which human beings had lived and worked in the world."
This verse also is one of those verses which point out that the lift hereafter will not only be a physical lift as it is in this world, but the body of every person also will be the same which he had in this world. If it were not so, it would be meaningless to tell the disbelievers: "We know very well whatever the earth consumes of their bodies and We have a Book which preserves everything. " (For further explanation, sec E.N. 25 of Surah Ha Mim As-Sajdah)
 

We know what the earth diminishes of them, and with Us is meaning in Urdu

زمین ان کے جسم میں سے جو کچھ کھاتی ہے وہ سب ہمارے علم میں ہے اور ہمارے پاس ایک کتاب ہے جس میں سب کچھ محفوظ ہے