1 Corinthians 15:28 says "And when all things shall be subdued unto Him, then shall the Son also Himself be subject unto Him that put all things under Him, that God may be all in all." God "is all, in all". Because God is all, the way we treat others is a direct correlation of how we are treating God. But how is this? How are we hurting God, if we hurt a person? How are we hugging God, if we hug a person? Let's go more in depth.

Understanding the Godhead

In Genesis 1:26, God said "let us make man in our own image". Who was God talking to? Who is us? "Us" is God the Father, God the Son, and God the Holy Spirit and together He is the Godhead (Colossians 2:9, 2 Corinthians 13:14). God the Father is a soul (Matthew 12:18), God the Son is the Word and body (John 1:1,14), and God the Holy Spirit is a spirit (John 4:24). And we are made in His image, so we also have a soul, body, and spirit (1 Thessalonians 5:23, Hebrews 4:12).

And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth. ~ Genesis 1:26

For in him dwelleth all the fulness of the Godhead bodily. ~ Colossians 2:9

The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen. ~ 2 Corinthians 13:14

Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: ~ Matthew 28:19

Behold my servant, whom I have chosen; my beloved, in whom my soul is well pleased: I will put my spirit upon him, and he shall shew judgment to the Gentiles. ~ Matthew 12:18

In the beginning was the Word, and the Word was with God, and the Word was God. And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth. ~ John 1:1,14

God is a Spirit: and they that worship him must worship him in spirit and in truth. ~ John 4:24

So God created man in his own image, in the image of God created he him; male and female created he them. ~ Genesis 1:27

And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ. ~ 1 Thessalonians 5:23

For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart. ~ Hebrews 4:12

Understanding How the Godhead Works Together

God the Father, being the soul of God, is what thinks. Yes, God thinks. In Isaiah 55:8 He says "My thoughts are not your thoughts". In fact, He says His thoughts are higher than our thoughts. God the Son, being the Word, is what speaks. In John 12:49  He says "I have not spoken of myself; but the Father which sent me, He gave me a commandment, what I should say, and what I should speak." God the Holy Spirit, being spirit, is what gives life. In Genesis 2:7 He says "The Lord God breathed the breath of life into man". Genesis 1:1-3 further shows that God the Father is the soul and thoughts of God, because He decided to create the heavens and earth. It also shows that God the Son is body/matter and speaks, because He said "let there be..." and it was so. It also shows that God the Holy Spirit is spirit and life, because it says the Spirit of God moved upon the face of the waters. The Godhead existed in the beginning, and together decided to create, spoke the desired thoughts, and then gave creation life. 

For my thoughts are not your thoughts, neither are your ways my ways, saith the Lord. For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts. ~ Isaiah 55:8-9

For I have not spoken of myself; but the Father which sent me, he gave me a commandment, what I should say, and what I should speak. ~ John 12:49

And the Lord God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul. ~ Genesis 2:7

Who knoweth the spirit of man that goeth upward, and the spirit of the beast that goeth downward to the earth? ~ Ecclesiastes 3:21

In whose hand is the soul of every living thing, and the breath of all mankind. ~ Job 12:10

In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light. ~ Genesis 1:1-3

Understanding How the Godhead Creates

Genesis 1:1 tells us that the very first thing God created was heaven and earth. Everything on earth is made from protons, neutrons, and electrons which form atoms. Atoms make up every element on earth like oxygen, hydrogen, iron, and many more. All of these elements combine in various ways to create different types of "matter". For example, hydrogen and oxygen combine to make water and the human body is approximately 99% of just six elements: oxygen, hydrogen, nitrogen, carbon, calcium, and phosphorus. But in the beginning, there was only the Godhead, so everything God made came from Himself. His own protons, neutrons, and electrons that He combined into atoms, to make up the elements He wanted, to create what He wanted. Everything within heaven and earth, the animals, seas, plants, humans, and heaven and earth itself, are not only made by God, they're made from God. God "is all in all" (1 Corinthians 15:28, Romans 11:34-36, 2 Corinthians 5:18). This brings a whole new perspective to "we are one body in Christ" (Romans 12:5), "what we do to others we do to Christ" (Matthew 25:40), and "love God and love others as we love ourselves" (Matthew 22:37-40). 

In the beginning God created the heaven and the earth. And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light. ~ Genesis 1:1-3

All things were made by him; and without him was not any thing made that was made. ~ John 1:3

In him was life; and the life was the light of men. ~ John 1:4

And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth. ~ John 1:14

So we, being many, are one body in Christ, and every one members one of another. ~ Romans 12:5

And the King shall answer and say unto them, Verily I say unto you, Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me. ~ Matthew 25:40

And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all. ~ 1 Corinthians 15:28

For who hath known the mind of the Lord? or who hath been his counsellor? Or who hath first given to him, and it shall be recompensed unto him again? For of him, and through him, and to him, are all things: to whom be glory for ever. Amen. ~ Romans 11:34-36

And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation; ~ 2 Corinthians 5:18

Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets. ~ Matthew 22:37-40

Conclusion

The definition of matter is "a physical substance, distinct from mind and spirit...". Whoever created the definition of "matter", may not even realize that they literally described the three parts of God Himself, and mankind since we are made in His image. And just as we are physical substance/matter/body, mind/thoughts/soul, and spirit/energy and still one person; God is physical substance/matter/body, mind/thoughts/soul, and spirit/energy and still one God. Just as our body, soul, and spirit can be separated and we still be one person (e.g. death); God's being can be separated and He is still one God. 

Many people in science believe God is separate from science but God is science. God is math, and language arts too; He created it all. He is everything. This is how God can be everywhere at once and how He knows all. How He can miraculously heal with the removal or addition of atoms required to bring wholeness. How anything we need is a small request to Him, because He is so intricately involved in every single detail. God said when we feed the hungry, take in strangers, cloth those that need it, and visit the sick and those in prison, we are actually doing it to Him. We are not God, or a god, we are a part of God. This is how our treatment of others is a direct correlation of how we treat God (1 John 4:20). This is only one reason why God loves us so much and does not want to see our soul perish (2 Peter 3:8-9). This is what it means for God to be all in all. 

For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him: and he is before all things, and by him all things consist. ~ Colossians 1:16-17

Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself. ~ Philippians 3:21

If a man say, I love God, and hateth his brother, he is a liar: for he that loveth not his brother whom he hath seen, how can he love God whom he hath not seen? ~ 1 John 4:20

Then shall the King say unto them on his right hand, Come, ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world: For I was an hungred, and ye gave me meat: I was thirsty, and ye gave me drink: I was a stranger, and ye took me in: naked, and ye clothed me: I was sick, and ye visited me: I was in prison, and ye came unto me. Then shall the righteous answer him, saying, Lord, when saw we thee an hungred, and fed thee? or thirsty, and gave thee drink? When saw we thee a stranger, and took thee in? or naked, and clothed thee? Or when saw we thee sick, or in prison, and came unto thee? And the King shall answer and say unto them, Verily I say unto you, Inasmuch as ye have done it unto one of the least of these my brethren, ye have done it unto me. ~ Matthew 25:34-40

But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day. The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. ~ 2 Peter 3:8-9