God has made a promise, and the writer gives believers words to say in response. Because God will never leave them, "we may boldly say, The Lord is my helper." Barnes says this speaks to times "when we scarcely know whence the supplies for our necessities are to come." He adds that the sentiment is found in Psalm 27:1 and Psalm 118:6, and that the writer offers it not as a formal quotation "but as language which a true Christian may employ." The ESV, like Psalm 118:6, ends with a question: "what can man do to me?" The KJV reads it as a statement of settled trust: "I will not fear what man shall do unto me."

The answer is built into the confession itself: "The Lord is my helper." If He is the helper, then what man can do is not the final word. Gill notes that what people can do has a limit: "the utmost of which is to kill the body." The KJV form of the sentence states the answer directly: "I will not fear."

These readers knew what people could do to them. The writer recalls that they "took joyfully the spoiling of your goods" (Hebrews 10:34), and they were told to remember "them that are in bonds" (Hebrews 13:3). So the call to be content and unafraid was not abstract. Barnes connects the words with Psalm 118:6, "The LORD is on my side; I will not fear: what can man do unto me?" Gill thinks they are drawn from Psalm 54:4, "Behold, God is mine helper." Gill also says that "every believer can set up an Ebenezer," the stone Samuel named "Hitherto hath the LORD helped us" (1 Samuel 7:12).

This verse shows the order of faith: God speaks first, and His people answer. "He hath said" (Hebrews 13:5) comes before "we may boldly say" (Hebrews 13:6). The believer's courage is a response to God's promise, not a feeling worked up from within. Matthew Henry's Concise Commentary says, "Men can do nothing against God, and God can make all that men do against his people, to turn to their good."

The setting is everyday life: money, contentment, and fear of loss (Hebrews 13:5). God's promise to stay is meant to free His people from grasping and from fear at the same time.