CLAIM: The author writes, “And again, ‘I will put My trust in Him.’ And again, ‘Behold, I and the children whom God has given Me’” (Heb. 2:13). This citation comes from Isaiah 8:17-18. Why does he cite it here?
RESPONSE: The context of Isaiah 8 is the destruction of Judah. Because the evil king Ahaz did not believe in God’s provision (in chapter 7), God was bringing judgment on the people. Aram and Israel were about to descend on Judah (Isa. 7:1-9). Will the people trust in God during this time, or will they turn to political powers? That is the context of Isaiah 8.
Isaiah declares that he will put his trust in God—not the armies of the neighboring nations (like Ahaz). Isaiah implores them not to fear the nations (Isa. 8:12) but to fear God instead (Isa. 8:13). God will either be your sanctuary and safety (Isa. 8:14), or he will be your stumbling block (Isa. 8:15).
It is in this context that Isaiah states how he and his children will trust the Lord—not the nations (Isa. 8:17-18). Thus the author of Hebrews cites this passage to show that God’s people in the past failed to have faith; will they make the same mistake in the present? This would be similar to a counselor to the President explaining military action in World War II. He might relate our leap of faith to take the beach of Normandy in the past, and relate this to a current military crisis in the present.
Moreover, since Isaiah (the faithful prophet) linked his faith with those of his children, the author links Jesus’ perfect faithfulness with his people. Guthrie writes, “Isaiah saw himself as linked with his children in the service of God, for he recognized that the children were ‘signs’ given by God. This identification of the prophet with his children as signs is paralleled in the writer’s thought by the close link between Christ and his people.” Just as Isaiah led his faithful remnant in this political crisis, Jesus leads his people through the ultimate fear and crisis of death (Heb. 2:14-15).
 Guthrie, Donald. Hebrews: An Introduction and Commentary (Vol. 15). Downers Grove, IL: InterVarsity Press. 1983. 95-96.