Obviously, all the Gospel writers, including Matthew, were very selective in the stories, teachings, and details they included in their narratives. The apostle John in particular was cognizant of the inevitable telescoping of his account of Jesus' life and ministry on earth:
And there are also many other things which Jesus did, which if they were written in detail, I suppose that even the world itself would not contain the books that would be written (21:25 NASB).
Normally, even in the best of historical books, there has to be
- selection of material
- deflection of other material
which results in
- a reflection of the truth, which necessitates
- a distortion of the truth, since a reflection is not the original light source!
Most Christians believe the Bible to be unique, however, in that while it contains historical facts and details, it is not your average textbook on history; rather, it is a special revelation of God which because of its supernatural origin contains not only true and accurate historical facts, but it presents them to its readers accurately, without distortion, and without error. Jesus, who incarnated the truth said very succinctly in his high priestly prayer in John 17,
"Thy word is truth" (v.17).
For these reasons and more, when we ask ourselves questions, the answers to which are not readily available because the information needed to answer the questions is simply not in a given biblical text in a particular Gospel, we do well to do the following:
See what the other Gospel writers have to say. A good tool in this regard is a harmony of the Gospels. I use Dr. Orville E. Daniel's fine A Harmony of the Four Gospels (published by Baker Book House in the US and Welch Publishing Co. in Canada; ©1986). In a harmony of the Gospels, you can tell at a glance where and how the Gospel writers differ in the details. The particular advantage of Dr. Daniel's harmony is that the story line, which includes all the details--some of which might be unique to just one Gospel writer--is in bold print. Thus by simply reading the bold print (which crosses back and forth between all four columns, one column for each Gospel). In this way, Dr. Daniel has given us a real harmony of the Gospels. I commend his work to you without reservation.
See what other writers of Scripture have to say, since quite often we can glean facts and insights from what they have to say about the material found in the Gospels. For example, we would not have known that Jesus said
"It is more blessed to give than to receive"
if Paul had not quoted Jesus in the farewell speech he gave to the elders of the church at Ephesus in Acts 20:35.
Seek guidance from the Holy Spirit, who can lead you into all truth (John 16:13). This does not mean that every question you have, particularly questions about the silences contained in Scripture, will be answered to your satisfaction. Nor does this seeking process mean "It's just me and the Holy Spirit." No, the Holy Spirit has gifted the church with Bible teachers and scholars who very often can elucidate the Scriptures for us by virtue of their calling, their gifts, and their hard work. Very often, they have already done the heavy lifting for us, and all we need to do is consult them when we are stumped.
Know when to move on, particularly when you are not finding answers. Perhaps years later you will discover the answer you have been looking for. If not, that is OK, since (and I repeat) the writers of Scripture were both selective and deflective in their choice of material. Rest assured, however, whatever found its way into the canon of Scripture is the only truth you will ever need.
I personally do not have a definitive answer to your two questions. I do, however, think that you may be conflating somehow Matthew's account of Jesus' Sermon on the Mount with the account of Jesus' miraculous feeding of the 5000, as found in all four Gospels!
I encourage you to compare and contrast the two events on your own to determine what makes them different. That Jesus did not, according to Matthew anyway, provide food for the hearers of his Sermon on the Mount, does not mean Jesus did not provide food. It may simply mean Matthew did not find that detail relevant to his telling of his story.
I'll conclude by listing some of the facts Matthew (and other Gospel writers) does give us about Jesus' great Sermon on the Mount. Perhaps by piecing them together, you will better understand the event, if only from Matthew's perspective.
Jesus' sermon may have been given only to the large crowd of his disciples, and not to those disciples and to "the great number of people from all over Judea" and elsewhere. Luke tells us that the crowds who came to hear Jesus also came to be healed of their diseases, since Jesus was healing all comers (Luke 6:17 ff.)!
Matthew tells us that Jesus indeed saw the crowds (I assume both the crowd consisting of his disciples and the crowd of people who having heard about Jesus came to where Jesus was, not only to hear him but to be healed by him), and that he "went up the mountainside," "sat down," and when "His disciples came to him," Jesus "Looking at his disciples" (Luke 6), "began to teach them saying . . ." (Matthew 5). In other words, the primary audience to Jesus' sermon may have been just the crowd of disciples, while the crowd of travelers were not part of that audience.
Matthew leads us to believe Jesus' sermon had an introduction, a development, and a conclusion (or beginning, middle, and end). He began with the Beatitudes, which could perhaps be the New Testament version (or equivalent) of the Ten Commandments! He developed his sermon by expanding upon each beatitude ("commandment"), thus putting "meat on the bones," as it were, of what he had merely previewed in his introduction.
- The beatitudes, then, could be considered the rules for his kingdom on earth;
- the development section could simply be a fleshing-out of how those rules should govern the everyday lives of his committed followers;
- and the concluding story of the two houses, one built on sand and one built on the rock, was Jesus' way of summing up what it means to truly hear his words and then put them into practice (Matthew 7:24 and Luke 6:47).
When Jesus had finished saying these things, the crowds were amazed at his teaching, because he taught as one who had authority, and not as their teachers of the law. When he came down from the mountainside, large crowds followed him (Matthew 7:28-8:1). This last bit of information should pique your interest, since Matthew tells us that when he descended the mountainside "large crowds" (not just a crowd of his disciples) followed him, in part, we assume, because they were impressed by his authoritative teaching. So was the sermon delivered to all the crowds or just to the crowd of disciples? Good question, yes?
The amount of time over which Jesus' Sermon was stretched is not given in the Gospels. Moreover, the factors (and facts) which framed the account of the provision of food to the 5000 men (and who knows how many women and children) at the miraculous feeding, were not the same factors at play at Jesus' Sermon on the Mount. This is not to say that Jesus did not provide, or could not have provided, food for the crowds who came from far away to hear him and be healed by him. It's just that none of the Gospel writers felt compelled by the Holy Spirit to include any information of that sort. That being the case, we should probably begin looking for "bigger fish to fry," of which there are many!