James, a servant of God and of the Lord Jesus Christ,
To the twelve tribes in the Dispersion:
Greetings.
Count it all joy, my brothers, when you meet trials of various kinds, for you know that the testing of your faith produces steadfastness. And let steadfastness have its full effect, that you may be perfect and complete, lacking in nothing.
James 1:1-4
James is the author of this letter. Who is this James? This is James, one of the brothers of Jesus. It's interesting that James is such a prominent member of the church since he initially didn't believe Jesus. We read about this in John 7: "For not even his brothers believed in him". In any case, here he is now and there must've been a big change for him to now be a follower of this same Jesus who he previously did not believe in.
This letter is written "to the twelve tribes in the Dispersion". The dispersion refers to the scattering of the Jewish people. We read of this happening in the Old Testament on more than one occasion. However, in this instance, it is probably referring to the dispersion of early Christians from Jerusalem due to persecution. The fact that he uses the word "dispersion" probably signifies these people as Jewish. In addition, we notice in the letter that they are Christians who he is addressing.
Beyond the greeting, the letter begins with James talking about trials. The recipients of this letter have certainly had their fair share of trials, so it is probably appropriate that James addresses this issue. However, it's interesting that James tells them to "Count it all joy" when talking about meeting trials. This is an odd thing to say. It's not as if most people would tell someone struggling with a terminal disease to take joy in this disease. But this is what James does.
Why does he do this? Well, he explains the reasoning: "for you know that the testing of your faith produces steadfastness". The trial has a purpose and it is for producing steadfastness. Other translations use different words here, such as "endurance" and "perseverance". Passing through difficulties will help one weather new storms that come. It is because of this building of ones perseverance that James says to "count it all joy". It is not the trial itself that one is to take joy in, but the result or fruit that will come from experiencing it. So, with this fruit of steadfastness that will grow, his readers are encouraged to let it fully grow and blossom. For it to have it's full effect is to result in you being "perfect and complete, lacking in nothing". Experiencing trials and growing in endurance will result in a great maturity beyond it's current status.
I can imagine that those words: "perfect and complete, lacking in nothing" could be taken too literally. One will be quite that, but that isn't to say that you will be perfect in the way that Paul has not yet and will not in this life reach perfection. We read this in Philippians 3:
Not that I have already obtained this or am already perfect, but I press on to make it my own, because Christ Jesus has made me his own. Brothers, I do not consider that I have made it my own. But one thing I do: forgetting what lies behind and straining forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus. Let those of us who are mature think this way, and if in anything you think otherwise, God will reveal that also to you. Only let us hold true to what we have attained.
-Philippians 3:12-16
He hasn't made it yet, but strives for perfection. I believe that when James talks about the steadfastness that results from experiencing trials, this is that which grows oneself towards perfection but one will never be perfect in this life. Instead, the perfection is probably a different kind of perfect than the one Paul is referring to in Philippians. Perhaps this is a perfection owing to one's own steadfastness through trials. However, that isn't to say that this person is perfect and never sins.
Anyways, it is a difficult thing to "count it all joy" when facing trials, but we are to do it because of the endurance gained through the experience. Let us look to the fruit and take joy in it.
Actually, going back, what kind of trails are these? Well, they are "trials of various kinds" as James says, but I think he is referring to persecution for following Jesus. These are people who are part of the dispersion and there was a lot of persecution of Christians in that time. He also specifically addresses them as "brothers", meaning brothers in Christ. So, this steadfastness or endurance produced through facing trials is not just any trial, but probably ones owing to the fact that you are following Jesus. Perhaps this is why in AMP, it says "And let endurance have its perfect result and do a thorough work, so that you may be perfect and completely developed [in your faith], lacking in nothing". Specifically, it is your faith in Christ that is pefect, developed and lacking in nothing as the AMP puts it.