Bookends are used to keep books together. They also metaphorically describe how we keep other objects together. In the gospel of Matthew there are two important kingdom bookends that help us define the contents of the Sermon on the Mount in Matthew 5-7.
IMPORTANT BOOKENDS
The first bookend is in Matthew 5:1-2 where Jesus sees the crowds and goes up to the mountain. Here his disciples gather around Him to listen to Jesus’ as He begins to teach them.
The second bookend is Matthew 7:28-29 where Jesus’ audience has expanded beyond His disciples to include the crowds. They have been listening in and are amazed at Jesus’ authoritative teaching.
These bookends tell us that what Jesus has to say is very important. We know this because just before the final bookend in Matthew 7:28-29, Jesus contrasts two groups of people.
In Matthew 7:24-25 He addresses those who listen and apply His words to their lives. Jesus describes them as wise builders who anchor their foundation upon a rock. Their building will stand firm in the storms of life.
In contrast, in Matthew 7:26-27 Jesus describes those who also listen but do not put His words into practice. These people are like unwise builders who place their foundation upon sandy soil. When the storms come their house will not survive.
BEATITUDE BOOKENDS
At the very beginning of the first bookend Jesus launches into 8 beatitudes that fall between two other bookends. The first tells His audience that being poor in spirit is the way to the kingdom of heaven (Matthew 5:3). The concluding beatitude addresses those 
who are “persecuted because of righteousness” for theirs is, once again, the kingdom of heaven (Matthew 5:10).
These bookends tell us that between them are listed the crucial qualities of people who are citizens of the kingdom of heaven. Those qualities include poverty of spirit, mourning over sin, meekness, righteousness, being merciful, having purity of heart, being makers of peace and suffering for the sake of righteousness.
THE VALUE OF BOOKENDS
The Sermon on the Mount is important material for followers of Jesus Christ for at least three reasons. First, Jesus said their application would make the difference between those who survive the storms of life and those who do not. Second, for those who are citizens of the kingdom of heaven, the sermon provides a roadmap to maturity in the kingdom.
The third reason is anchored in the next-to-the-last parable Jesus used to underline their importance. In Matthew 7:21-23 Jesus tells us that there will be people who appear at Judgement Day, thinking that they are, indeed, citizens of the kingdom of heaven. They will come before Jesus pointing to the many things they have done to verify their eternal citizenship. Jesus’ shocking response to them should be sobering to us all as He says, “I never knew you. Away from me, you evildoers!” (vs. 23).
CONCLUSION
Perhaps there could be no greater tragedy than to go through life with a false sense of confidence in one’s salvation only to find, in the end, that one had missed the entire point of kingdom citizenry: knowing Christ and being known by Him. Herein lies the power of the Sermon on the Mount.