V 6.
These are our orders to you, brothers, in the name of our Lord Jesus Christ:  hold aloof from every Christian brother who falls into idle habits, and does not follow the tradition you received from us.
NIV.  In the name of the Lord Jesus Christ, we command you brothers, to keep away from every brother who is idle and does not live according to the teaching you received from us.

Paul was talking here about people who were able to work but who decided not to work.  In Australia people like this are sometimes labelled 'dole bludgers' - people who continue to accept Government welfare payments (used to be known as 'the dole', but now called by some more politically correct title - which tends to change almost as often as the names of Government departments <g>!) when they are fit and well enough to get work of some kind, even if it's not their ideal career choice.

The attitudes to work and employment are different in different generations.  People of my age group (yes, us oldies) tend to think it's right and proper to be employed until you're 65 years of age - or whatever the official 'retirement age' is - even if it means you have to accept any kind of work that's available and that you're capable of doing whether it's the kind of work you prefer or not.  Then, after you retire, you continue to work almost as hard in some voluntary capacity. Younger people seem to take the attitude that they should be able to do work that's satisfying and fulfilling and they should wait until such work is available - and that the community should support them until that work arrives.

The Australian government instituted a 'work for the dole' scheme, where people who are receiving welfare may be required to undertake voluntary work in some community project while they are receiving that welfare.  This scheme is most unpopular with some people as they see it as exploiting the unemployed.

Paul was suggesting that the church community should not encourage people who refuse to work for their living when they are really able to do so and when there is work available.  He was not suggesting that the church should not support the elderly and infirm who were unable to work or those who genuinely look for work and can not find employment of any kind. I have a son who was out of work for many years looking for his ideal job and who eventually decided he should take any employment offered.  His comment was that he realised that there is work you do because you love it and there is work you do to earn a living - and they are not always the same jobs.

Quest Study Bible note: p 1639.  Why were idle Christians such a danger?  For at least three reasons:
1)  Their lives were characterised by laziness - a sinful attitude that could spread to others.
2) Other believers felt obligated to provide for the idle Christians, severely draining the church's resources.
3)  The idle Christians gave a warped view of Christianity, that those who are most heavenly minded focus only on the return of Christ.  Meanwhile, their neglect of practical matters undermined the church's credibility and witness.

New Bible Commentary, p 1290.  .....the problem of certain members of the church living in idleness off the generosity of others went back to the time when the church was founded (v 10). Evidently there were people who were living on the poverty line and relied on the gifts of richer people.  The belief that the day of the Lord had come may have encouraged their attitude.  This way of life was giving the church a bad name, and therefore Paul speaks out strongly against it.  V 6 begins with a sharp command, backed up by the authority of the Lord, that the church members must avoid those whose conduct is unworthy.  The latter are not to be deprived of their place in the church, but there is to be a certain distancing from them so that they recognise that their conduct is not acceptable or in accord with the established teaching of the church handed on by Paul.

Vs 7 - 9.
You know yourselves how you ought to copy our example: we were no idlers among you; we did not accept board and lodging without paying for it; we toiled and drudged, we worked for a living night and day, rather than be a burden to any of you - not because we have not the right to maintenance, but to set and example for you to imitate.

Paul usually worked at his trade - tentmaking - when he travelled around and stayed in a town or city where there was a young church so that the local people wouldn't feel they needed to support him. And he certainly did this in Thessalonica.  No Christian should be a burden on others, even if they are prepared to provide support in times of need.

In some Christian denominations  even the pastor works in a secular job to support himself and his family rather than expecting his congregation to fully support him - thus providing a model for the people in his church.  Most 'mainline' denominations, I think, take the attitude that the pastor more than earns his keep and therefore should be supported by the church!  Paul also believed that churches had an obligation to provide for their teachers (1 Corinthians 9: 4-14). In Thessalonia, Paul made the decision not to insist on this right, so he could set an example to the people.

V 10.
For even during our stay with you we laid down the rule: the man who will not work shall not eat.

God gave each of us talents, gifts and skills which he expects us to put to good use.  When we refuse to work, we are not making the best of our talents and skills.  Jesus talked about this when he told the story of the people who were given talents (in that case, money) to work with while their master was away and how displeased the master was on his return with the one person who hadn't used the money he'd been entrusted with to make more.  He hid his money and returned to the master exactly what he'd been given to take care of.  The other two people had invested their money wisely and made a profit for the master.  Since they'd used well what the master had given them, they were given more to use. (Matthew 25: 14 - 30)

New Bible Commentary, p 1290.   although the command has the form of an instruction to the well-off not to give to the idle hungry people, it is primarily meant as a warning to the latter.  It is worth repeating that the proverb-type saying applies to people who are unwilling to work, not to those who have no opportunity, and is therefore not an argument against welfare provision for the unempoyed

V 11.
We mention this because we hear that some of your number are idling their time away, minding everybody's business but their own.
NIV.  We hear that some among you are idle.  They are not busy; they are busybodies.

When we haven't enough to do, or when we don't have a purpose in life that working gives - whether it is paid employment or volunteer work - we tend to get into mischief!  Gossip starts when people don't have anything better to think about.

V 12.
To all such we give these orders, and we appeal to them in the name of the Lord Jesus Christ to work quietly for their living
NLT.  In the name of the Lord Jesus Christ, we appeal to such people - no, we command them: Settle down and get to work.  Earn your own living.

Paul repeats his instruction and reinforces it by giving it in the name of Christ.  those who are able to work must do so and stop sponging off other people and making a nuisance of themselves.