In Hebrews 11:1 we find the definition of faith: “Now faith is the substance of things hoped for, the evidence of things not seen.” The NIV translation says, “Now faith is being sure of what we hope for and certain of what we do not see.”
What does Scripture say that faith is? First, it says that faith is the substance. It is being sure of whatever it is that we hope for. Faith is so real it is called substance. Substance is the material of which something is made, the building blocks of it. Your faith is the substance, the building blocks of God’s promises! The Greek word used for this particular word substance is hupostasis. Hupostasis means “that which stands under,” the basis of something or that which supports the thing.
To understand further, we can look at the other ways the word substance, or hupostasis, is used in the Bible. In Hebrews 1:3 NASB it says, “He [Jesus] is the radiance of His glory and the exact representation of His nature.” The Greek word used here for nature is the same word substance or hupostasis. In other words, this verse is saying that God, who is eternal and invisible, became visible—became of substance—in Jesus Christ. Jesus is the exact representation of the Invisible, Almighty God. The substance—Jesus—is the real God in human form. Just like Jesus is the substance of God who is invisible, faith is the substance of those things that we hope for that are invisible.