Epistle of James is the letter that James sent to "the  twelve tribes
in the Dispersion". James himself and the twelve tribes were under the
cross when this letter was sent. So James teaching them especially
about how they must live when they meet trials of various kinds.

The word "trial (Strongs: 3986)" is used twice in this letter (1:2,
12), but if you read the passage in the original language, you will
notice very similar word "tempt (Strongs: 3985)" in 1:13 and 1:14. So
for that reason, the phrases "when you meet trials of various
kinds..." and "Let no one say when he is tempted..." refers to the
same time.

In 1:2, what James teaching about the trials is to "count it all joy".
Because by going through trials with steadfastness, their faith will
be tested (1:3) and make them perfect and complete at the end (1:4).
In 1:13, James is teaching not to say that they were tempted by God
when they were tempted. Because He will never tempt man. But the
temptation comes from man's lust and sins. Therefore James is teaching
them not to be deceived which is to be patient in the trials.

Why is James teach people who is in the trials not to be deceived and
to be patient? Because the patient will make them perfect people and
they will not lack in anything but will be filled with every good and
true thing which will be given to us from heaven. So in this letter,
it is clear that the keywords "endurance, patience (5278/1:12, 5:11,
5281/1:3, 4, 5:11)" and "perfect, complete (1:4, 17, 25, 3:2)" have an
important link with the them of "trials".

Paul used the word "endurance" or "patience" 5 times in this letter.
And in the context, he is teaching the twelve tribes to endure
temptations. And the reason is clear. Because as he wrote in 1:12 and
5:11, blessings will be given to those who undergoes the trials. This
is because, people who goes through trials and approved by God will
receive the crown of life which the Lord promised. For that reason, it
is clear that the trials are not given just for affliction but for joy
that comes after it.

When James talks about the patience in the days of trials. He used the
story of Job as a metaphor. Because in this story, not only that Job
was affected by a bad disease but he also lost his family, fortune and
even his friends abandoned him. But by undergoing this trial, his
faith was tested and his endurance brought him the blessed end by
God's mercy. By reading the story of Job, the passage "And let
steadfastness have its full effect, that you may be perfect and
complete, lacking in nothing." will be more close to us. Job was
already called "the perfect man" by God himself before the days of
trials. But by his patience in the affliction he became even more
perfect. So when James taught his brothers in Christ in 5:10 "As an
example of suffering and patience, brothers, take the prophets who
spoke in the name of the Lord.", he gave  the story of the
steadfastness of Job as an example.

People who will be perfect by the steadfastness in the trials are also
called "people who lacks in nothing". This is the saying that comes
out in 1:2-8, but you will also find that there are people who "lacks
wisdom". And they are the complete opposite of those who "lacks in
nothing". The important keyword in this context is "wisdom". Because
people who lacks in nothing are those who does not lack in wisdom in
the contrast to people who "lacks wisdom" that comes out in 1:5. And
those who lacks wisdom are taught to pray to generous and gracious God
in faith for the wisdom. God will give to those who believes and asks
for it. The specific list of what wisdom is comes out in 3:17 as "the
wisdom from above". Which is "pure, then peaceable, gentle, open to
reason, full of mercy and good fruits, impartial and sincere (3:17)".
With these points in mind, we now know that people who is "perfect" is
the one who does not lack in wisdom and do these things that are
listed in 3:17.

These things are what James wrote to the twelve tribes about meeting
the trials. And it is interesting that he used the phrase "my beloved
brethren" 15 times to call the twelve tribes. Because this commandment
that James taught them to be patient in trials has to be kept among
the church and not only among the individuals. So James taught them
not to grumble against one another or to speak evil against one
another. And what we are taught to do is to confess our sins to one
another and pray for one another (5:16).