NOTES for Mat 7:21-23
The desire for firmness, for a reliable ordering of life, belongs to almost every person. To a significant degree, many of our opinions and actions are explained by this desire. As Matthew concludes the account of the Sermon on the Mount, he includes in it today's parable of the houses built on sand and on rock: in it the Lord speaks precisely about this firmness of life.
This parable sounds like a kind of conclusion to the whole Sermon on the Mount. Some Protestants like to call the Bible an instruction manual for human life, and we see that this view is not without foundation. The whole Sermon on the Mount speaks of what is needed in order to be alive in the true sense of the word. And the concluding parable emphasizes that it is about real life, the kind no calamity can collapse.
This does not mean that there will be no calamities, but a person who lives by Christ's word and fulfills this word is stronger than any adversity. Moreover, by Christ's victory we become stronger with Him than death itself. Even hardships appear for such a person not as a depressing, oppressive accident, but as the way of the cross by which we can follow God.