As our Lord wrapped up His Sermon on the Mount, He emphasized the need to be doers and not just hearers (cf. John 13:17; James 1:22). Human nature is such that most who heard His powerful words that day would walk away impressed but not changed; most would hear but not do. Thus, Jesus challenged His listeners to action. He wants all to be wise men who hear and do; such can be described as building one's "house on the rock."
The hills of Palestine were subject to heavy rainstorms (and even floods) at certain times of the year. Water rushing down the ravines would soon undermine a foundation if the house was built on sand. But, if a house was founded on rock, it was safe from such. In like manner, one who builds his character (i.e., his "house") by hearing and doing what Jesus teaches will stand approved of God on the Day of Judgment--his house will not "fall".
It should be noted that the difference between these two builders is not in their craftsmanship or quality of materials used. It can be assumed that both men do their best in building their "house." However, the difference is that one chose his foundation wisely while the other was careless. Luke 6:48 makes this point clear.
Friends, when the trials of life come (and they will come), there is only one way to guarantee success--your life must be built on Christ, the only solid foundation, and you must remain faithful to Him (cf. I Cor. 3:11; Matt. 10:22). One who builds his life on Jesus Christ by obeying His revealed will, the New Testament, will have nothing to worry about when the floodwaters of life strike.
Jesus ended His sermon, not with words of comfort, but with words of tragedy - "And great was its fall." Even a single lost soul is a terrible waste in the eyes of God.
The people were astonished at Jesus' teaching because "He taught them as one having authority, and not as the scribes" (Matt. 7:28,29). Jesus did not quote rabbis to establish the things He was speaking, which was the common practice of the day. Instead, He merely spoke the truth.
Dear listeners, how great a loss it would be for one to never hear or study the Sermon on the Mount! But, there is an even greater loss: to fail to heed the truths contained therein once they are heard! May we always endeavor to be diligent hearers and faithful doers of God's word!