Forward-looking faith in God and in the sure fulfillment of His promises through Christ preserves our souls (Heb. 10:37–39). Through such faith, we inherit eternal life (John 3:16). By faith, we persevere instead of committing the apostasy that the author of Hebrews warns us against.
Building on this idea, the author of Hebrews in chapter 11 describes what faith is and what it produces. He begins by defining faith: “Faith is the assurance of things hoped for, the conviction of things not seen” (v. 1). Let us consider the second part of the definition first. Note how faith operates with respect to the invisible, with respect to those things that are not evident to our senses, with respect to “things not seen.” Faith is not sight. One day, we will see the Lord face-to-face (1 John 3:2). At that point, we will not need faith, but until that day faith is required. As the conviction of things not seen, faith is the certainty that what is not yet visible—the final fulfillment of God’s promises—is real and is coming. John Chrysostom comments, “Faith then is seeing things not plain . . . and brings what are not seen to the same full assurance with what are seen.”
The first part of the definition of faith given in Hebrews 11:1 tells us that “faith is the assurance of things hoped for.” A more literal translation of “assurance” in this case is “substance.” Our faith gives substance to the things for which we hope. It is one of the evidences that the things we do not see—for example, Jesus sitting on the throne in heaven, the coming renewal of all creation—are real. Of course, belief that something is real is insufficient by itself to make it real. That is why Scripture gives us historical testimony and other objective evidences of the unseen. Nevertheless, present faith is one confirmation that the things for which we hope actually exist and will actually be accomplished according to God’s plan.
Having defined faith, the author of Hebrews next tells us that it is the key to the commendation of the old covenant saints (v. 2). The Word of God praises people for their obedience, but any good that can be found in their obedience is grounded in the fact that they trust the Lord and are moved and empowered by Him to service. John Calvin writes, “However excellent were the works of the saints, it was from faith they derived their value, their worthiness, and all their excellences; and hence follows what he has already intimated, that the fathers pleased God by faith alone.”