The sermon on the mount is a set of teachings from Jesus that have been grouped together in a section of Matthews gospel (chapters 5-7). The teachings are also in the other gospels (in various forms). Scholars like to get all hot under to collar debating whether Jesus sat down or stood up to preach and how many actually listened. 

There is historical interest to finding answers to these questions but realistically we aren't going to answer them in a way that makes everyone happy unless someone invents a time machine to go back and find out.

The gospel writers all arrange their material to make points so it becomes impossible to say whether this sermon was written down as presented or whether Matthew gathered together several sermons into one place.

Sadly too many Christians gets caught up in this kind of detail and then fail to get the point of what Jesus was trying to teach us anyway. What methods Jesus used for preaching are not the point of the sermon.

The sermon offers guidance for the follower of Jesus to understand what life in the kingdom of God is supposed to be like (a kingdom is where a King rules so kingdom of God - sometimes 'kingdom of heaven' in the bible - is where God rules).

Jesus makes it very clear that he is not intending to offer a new set of rules that simply replace the ones found in the ten commandments but that through the following of his guidance we can learn to love, forgive and enjoy life.

One of the complications with Christianity is that Christians believe that the way to get a good relationship with God is to rely on the loving and forgiving nature of God and not worry about trying to prove ourselves through the following of certain rules (what Christians sometimes call being saved by grace).

However once we have gained that good relationship with God through our faith in God we then need to commit ourselves to living life with God in charge. We commit ourselves to letting God be our monarch and living a life in God's kingdom.

We could take the line of saying that all we have to do is to love God and forget about the rest (as St. Augustine once did) but this doesn't answer all of our questions. We are people who have to live in a practical world and so we need some practical guidance.

Because Jesus understood this he gave us guidance about what kingdom living is all about - guidance which we find in the sermon on the mount.

So if you ever wonder what a Christian should live like then you should turn to the sermon on the mount. Like all things you read in the bible you shouldn't read things in isolation. The best way to understand what a passage or verse from the bible says is to measure it against everything else the bible says.

Does this teaching apply to people who are not Christians? The easy answer is yes, because this is how God intends us all to live, but the less easy answer is that each person must choose whether to live like a member of God's kingdom or not. Christians cannot force people to live this way they can only hope that others will want to live this way when they see the difference it can make in the Christians life.