Early in my professional life I saw firsthand how critical the foundation of a building is to its structural success. In the early 1980’s I worked in the downtown financial district of San Francisco, a city built upon very unstable soil and prone to severe earthquakes. The “Great Quake of 1906” taught the San Franciscans just how devastating it can be when buildings are not properly built on solid foundations. I was reminded of this fact every day that I walked to work and saw the workmen working month after month in a huge hole on the foundational system of a future high-rise skyscraper. It would get annoying walking on temporary sidewalks and past plywood barricades as they labored on, preparing the site with steel rebar, concrete, and foundation forms. Then one day, as if out of nowhere, the building’s skeletal structure would begin to appear, revealing the soon-to-come enormous building that was going to occupy this part of the skyline. No matter how impressive the building would one day be, its structural integrity was all dependent upon the firmness of the foundation.
The necessity of having a firm foundation is a lesson we all need to learn, especially when it comes to our spiritual lives. A building’s structural integrity is dependent upon the types of materials that are used and the type of foundation it is built upon. In the same way, we need to be very careful what we are building our spiritual work on, and to take heed how we are building. Jesus instructed his followers to make sure that they not only heard his words, but also put them into practice. If they did then they would be like a wise man that had laid his foundation on a rock.
Matthew 7:24 and 25
(24) Therefore everyone who hears these words of mine and puts them into practice is like a wise man who built his house on the rock.
(25) The rain came down, the streams rose, and the winds blew and beat against that house; yet it did not fall, because it had its foundation on the rock.
For a long time I gave myself a pass on ungodly behavior, largely because I felt righteous in my knowing (hearing) Jesus’ words. Hearing and knowing is where we need to start, but it must be followed by practice. We are not building on the firm foundation of Christ unless we are “doing” what he said to do. Truth in doctrine is a prerequisite for truth in practice, but the point of hearing is doing.
Do not merely listen to the word, and so deceive yourselves. Do what it says.
Not only are we building as unskilled tradespersons when we do not build with truth, we are also building on a wrong foundation. Every building contractor knows that if the foundation is wrong then the house cannot succeed. A number of years ago I hired a contractor to add a porch on the back of my house. Unfortunately, during the process of installing the foundation, one of the tradesmen made a mistake resulting in the foundation being over three inches out of square. The error at this most fundamental stage of construction transfers into headaches and difficulties at each subsequent stage of building. It had to be fixed or I would end up with a porch that was crooked, which is something no one wants. If we do not take care to build on the foundation of Christ, the only firm foundation there is, our work will be in vain because our building will not last. It will not endure because it is being built on a very unstable and shaky foundation. Jesus said it is like building on sand, the worst of all types of load-bearing soils, and the result is that what we built will one day come crashing down.
Matthew 7:26 and 27
(26) But everyone who hears these words of mine and does not put them into practice is like a foolish man who built his house on sand.
(27) The rain came down, the streams rose, and the winds blew and beat against that house, and it fell with a great crash.
God has given us the Rock upon which each of us can build. The structural integrity and suitability of Jesus as solid foundational material has passed the most rigorous examination possible. God confirmed the acceptability of Jesus as the proper foundation when he raised him from the dead, and he is the only foundation that meets the Master Building Inspector’s stamp of approval.
1 Corinthians 3:11
For no one can lay any foundation other than the one already laid, which is Jesus Christ.
I am building on sand whenever I rebel against God by sinning. Every time I “want it my way” instead of His way, or whenever I attempt to stand in my own sense of self-righteousness on my works, I again build on unsound ground. Any foundation other than the foundation of Christ is nothing but quicksand that will swallow us up and make all of our work worthless. When we pursue holiness, we are not like the wicked or ungodly whose houses will one day fall; rather, we are standing upon The Rock.
Wicked men are overthrown and are no more, but the house of the righteous stands firm.
Most builders I know hate having to redo their work. It is very frustrating to build something and then see it fall apart or rot. I love knowing that when I pursue Christ and practice his words, I am constructing something that will endure. It will not rot, fade, rust, or ever corrupt away.  Not only will it never perish, but it also cannot be destroyed when Christ tests it, because it is fireproof.
1 Corinthians 3:12-14
(12) If any man builds on this foundation using gold, silver, costly stones, wood, hay or straw,
(13) his work will be shown for what it is, because the Day will bring it to light. It will be revealed with fire, and the fire will test the quality of each man’s work.
(14) If what he has built survives, he will receive his reward.”
When I read the construction specifications of the Tent of Meeting (Tabernacle) that God gave to Moses, the blueprint so to speak, I am amazed at the details and precision that He laid out. He enumerated to Moses every detail He desired: its size, materials, colors, and manner of putting all the pieces together.  Every tradesman knows that the success of a construction project is found in the preplanning of the details and specifications. No contractor can be expected to deliver to the owner what he or she desires if they do not communicate their “wants” up front. God knew what He wanted and He communicated it to Moses; then it was Moses’ responsibility to make sure it happened. In a similar manner, God has communicated to us through Jesus His desire for the type of building we are to construct.
1 Peter 2:4 and 5
(4) As you come to him, the living Stone—rejected by men but chosen by God and precious to him—
(5) you also, like living stones, are being built into a spiritual house to be a holy priesthood, offering spiritual sacrifices acceptable to God through Jesus Christ.
He has clearly communicated to us the building plans and given us the tools and materials with which to build. God and Jesus have done their part, now it is up to us to do ours. When we put Christ’s words into practice we are building upon the firm “foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone” (Eph. 2:20).
When the Israelites had finished building the Tent of Meeting, Moses inspected their work and blessed it because they had done the work just as Yahweh had commanded (Exod. 39:42). In the same way, we have the responsibility to build just as our Lord has commanded us. We begin by establishing Christ as our foundation when we make him our Lord.  We then build upon a solid foundation when we transform ourselves by putting on his character, which is the pursuit of holiness. We erect a lasting edifice whenever we discipline ourselves to live like Christ, according to God’s ways, not the ways of the world. We all sin, and when we do we should be quick to repent and confess our sin. And when others sin against us, we cannot be grudge-holders, but rather we must extend forgiveness, getting rid of all malice and bitterness. We must first know the way of our Father, learning His words, and then have the character and courage to do them. Then we can be the heart of God to a spiritually malnourished world.
Every loving act we do adds another enduring piece to our masterfully erected building. Some buildings are made out of weak materials and will not last. Let’s make sure that through our godly words and deeds we employ the highest quality materials. When we do, we have the promise that what we build will last, because we are Building Upon the Firm Foundation.
 Matthew 6:19-20: “Do not store up for yourselves treasures on earth, where moth and rust destroy, and where thieves break in and steal. But store up for yourselves treasures in heaven, where moth and rust do not destroy, and where thieves do not break in and steal.”; 1 Peter 1:3-4: “Praise be to the God and Father of our Lord Jesus Christ! In his great mercy he has given us new birth into a living hope through the resurrection of Jesus Christ from the dead, and into an inheritance that can never perish, spoil or fade–kept in heaven for you…”
 Scholars have noted that the Bible must not contain all of the information necessary for building the Tent of Meeting, but it is clear from Exodus that God gave the details to Moses.
 Romans 10:9 and 10: “That if you confess with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. For it is with your heart that you believe and are justified, and it is with your mouth that you confess and are saved.”