Take care, brothers and sisters, that none of you may have an evil, unbelieving heart that turns away from the living God. But exhort one another every day, as long as it is called “today,” so that none of you may be hardened by the deceitfulness of sin. For we have become partners of Christ, if only we hold our first confidence firm to the end. As it is said, “Today, if you hear his voice, do not harden your hearts as in the rebellion.” Now who were they who heard and yet were rebellious? Was it not all those who left Egypt under the leadership of Moses? But with whom was he angry forty years? Was it not those who sinned, whose bodies fell in the wilderness? And to whom did he swear that they would not enter his rest, if not to those who were disobedient? So we see that they were unable to enter because of unbelief. (Hebrews 3:21-19, NRSV) The book of Hebrews was written as a spiritual guide for the new Christian church. While the overall theme of this book is that Jesus Christ is the sole source of God’s grace for Christians, this passage in particular deals with unbelief. The writer refers to a passage from the Psalms with which his presumably largely Jewish audience would be familiar. Using the experience of the Israelites who escaped Egypt only to fall into idolatry while awaiting God’s deliverance, the writer tells us to guard against such unbelief by encouraging each other in faith.