Hebrews 11:1 (KJV) says, “Now faith is the substance of things hoped for, the evidence of things not seen.” In order for it to be the “substance” of something hoped for there must be something substantive (like a promise) that was given in the past, that we could have hope for the fulfillment of in the future. Since the future has not been seen yet, our evidence for the promise being fulfilled is based on our trust that God will do it because he promised to do it. We must trust that God is faithful to his promises.
Romans 10:17 says faith comes by hearing and hearing the word of God. Abraham heard a promise from God and that was the substance that he could hope for. He heard this promise when he had no descendants and the initiation of that promise (the birth of his seed) was fulfilled when he had Isaac, 25 years after the promise was given. The rest of the promise was held onto by Abraham, Isaac, and Jacob, and passed down to Moses who trusted God to lead the Israelites out of Egypt and into Canaan. Abraham was told in Genesis 15:15 that he would not see the inheritance of the land, but he could trust that it will be done in the future. Abraham was given a promise from God that his seed (descendants) would inherit Canaan. Neither Abraham, Isaac nor Jacob saw that promise fulfilled but they trusted that it would be in the future (Heb 11:8-10). Then over 430 years later, Moses was there to see the fulfillment of that promise, even though he died before he could partake in it (Deut 4:21-23).
Trust is synonymous with the word faith, and we are to trust God’s promises from his word for our lives. Even before they are seen, it’s the substance of God’s promises from his word that we are to hope for and that is the evidence we are to trust in that will be eventually seen and fulfilled in the future. No one can have anything to hope for until they have heard his word because according to Romans 10:17 faith comes from hearing God’s word. This is why the gospel (good news) must be spread, to give people hope in the promise of eternal life. In previous verses, Romans 10:14-15 says, how can they [anyone] call on him [God] to save them unless they believe in him? And how can they believe in him if they have never heard about him? And how can they hear about him unless someone tells them? And how will anyone go and tell them without being sent? Then Paul quotes Isa 52:7 saying, “How beautiful are the feet of messengers who bring good news.”
Finally, Hebrews 11:6 says that without faith it is impossible to please God because those that come to God must believe that he is whom his word says he is, and that he is a rewarder of them that diligently seek him. The previous verse mentions Enoch (from Genesis 5:22-24) who instead of dying was simply translated to heaven because of his walk with God. That personal walk with God was built on deep faith and a desire to seek God. In Matt 6:31-34, Jesus himself says in order to get the fulfilled promises of God to provide for our needs, we must seek him. We aren’t just supposed to have trust or faith in Him for the things we need, but we must also trust in God’s leading us in his will for our lives like Abraham trusted God when he moved to Canaan.