Introduction

 Al-Hashr is the assembling and collection of different things to one place. The Gathering of the Day of Resurrection is the assembling of creation in one place for their accounting and judgment between them.

Allah named the Day of Resurrection the Day of Assembly because Allah will assemble all of the slaves in it as he says,

That is a Day whereon mankind will be gathered together, and that is a Day when all (the duellers of the heavens and the earth) will be present.

Surah Hud: 103)

Everyone will be assembled, the first and the later generations. This is as Allah says,

Say (O Muhammad salla alayhi wa sallam): (Yes) verily, those of old, and those of later times. All will surely be gathered together for appointed Meeting of a known Day. (Surah Al-Waqiah: 49-50)

Nothing incapacitates Allah, Wherever Allah takes the life of His slaves, He will bring them back from that space and atmosphere, whether it is from the darkness of the ocean floor, from the crust of the earth or from the bellies of birds, beasts and fishes,'. With Allah, all of these are the same. Allah says,

Wheresoever you may be, Allah will bring you together (on the Day of Resurrection) Truly, Allah is Able to do all Things. (Surah Al-Baqarah: 148)

His knowledge encompases them and He does not forget anyone. Our Lord says,

There is none in the heavens and the earth but comes unto the Most Beneficent (Allah) as a slave. Verily, He knows each one of them, and has counted them a full counting. And everyone of them will come to Him alone on the Day of resurrection (without any helper, or protector or defender. (Surah Maryam: 93-95)

Yes, Allah keeps count of all creatures. He knows their male and their females, their young and their old. The keeps count of their deeds, breaths and words, all; of them are under the subjugation and authority. Everyone will come to Allah alone and He will judge among His creatures as He wills,

And we shall gather them all together so as to leave not one of them behind. (Surah al-kahf: 47)

When resurrection is established, Allah will gather all of the creation in one pleace.

Proof on The Gathering, 

The affirmation of the Gathering is in various places in the Book of Allah and among them are the Following, and we shall gather them all together so to leave not one of them behind. (Surah Al-Kahf: 47)

Allah also says,

Say (O Muhammad salla alayhi wa sallam): /Yes) verily, those of old, and those of later times. All will surely be gathered together for appointed Meeting of a known day. (Surah Al-Waqiah: 49-50)

He says,

and We shall collect them all together. (Surah Al-Kahf: 99)

The Messenger of Allah salla alayhi wa sallam said;

Allah will gather on the Day of Resurrection, the first and the last, in on plain and they will be made to hear a caller and their sight will percolate.

The Description of The Gathering

The creation will be gathered on the Day of Resurrection on a crystal white land. The Messenger of Allah salla alayhi wa salla said,

The people will be gathered on the Day Of Resurrection on a white land like a pure load of bread. It will have no landmarks for anubody ( to make use of).

A pure load of bread is bread that is made of pure fine flour of weat or barley and free from adulteration and chaff.