Hebrews 1:3a

Before I begin, you need to know this portion continues to blow my mind... Daily.

1:3
"He is the radiance of the glory of God and the exact imprint of His nature and He upholds the universe by the word of His power. After making purification for sins He sat down at the right hand of Majesty on high."

"He is the radiance of the glory of God." The Jews called the ark, 'His glory' because in it they had the representation of God dwelling among them. "So he who had revealed the will of God to them was none other than he who had dwelt among them from the beginning, representing in all things the person of the Father, being typically revealed to them as the radiance of the glory of God. (Owen)"

"The exact imprint of his nature." The Son is the Father. "The exact imprint of the Father is the Father himself." Jesus must, be, do, and have exactly what the Father is, does, and has or he cannot be our representative head. Jesus must be the God-Man. Fully God to live the perfect life. Fully man to make propitiation for us.

"And he upholds the universe by the word of his power." Upholds, sustains, supports, carries along to a single end. This sustaining work is the only thing that keeps creation from falling back into nothingness at any one moment. All this is done by his word. "His enabling word (Knox)." "The 'word' is thought of as active and powerful... The 'word' is not empty. It has force. It does things (Leon Morris)."
With a word the universe was created, and with a word it is sustained by the powerful (dynamis = dynamite), effectual, change causing word of God. When God speaks things happen. Not little trifles (although they are included) but universes, Everests, Grand Canyons, single celled life, animals, people, spider webs, leaves, salvation happens from utter nothingness. The same powerful word that, created everything brought about our salvation (Rom. 1:16) When God speaks change happens. The dead are raised to life. The blind see. The deaf hear. The captives go free. The word of God will not return to him void.

Side note: Practically speaking, Christ's word sustains us, all the time... Meaning that while we are sinning, while we are thankless, while we are loveless; while we are dead (in our sins) Christ sustains us. While people interact and go about their lives in complete objection to God he sustains them. While they live lives of rebellion against him, he sustains them… While we are living lives of rebellion against him, he sustains us!
Birds fly, leaves grow, rain falls; we feel, and hear, and see, and taste simply because Christ says, "BE!" For no other reason do we exist apart from God's mere will.
Therefore, as a Christian, my view of others should (and indeed has) change dramatically. For how can I know that God sustains all things, and still not love them? God sees mankind as worthy of upholding, if only for the purpose of his glory, so I should see them as worthy of love. But more often than not I see my love to them as an obligatory duty, not an overflowing of love. So here, in this verse, is a wellspring of love for others, that Christ sustains them, and therefore, if for no other reason, I should love them, because he loves them.