Knowing this, that the trying. We now see why he called adversities trials or temptations, even because they serve to try our faith. And there is here a reason given to confirm the last sentence. For it might, on the other hand, be objected, "How comes it, that we judge that sweet which to the sense is bitter?" He then shews by the effect that we ought to rejoice in afflictions, because they produce fruit that ought to be highly valued, even patience. If God then provides for our salvation, he affords us an occasion of rejoicing. Peter uses a similar argument at the beginning of his first Epistle, "That the trial of your faith, more precious than gold, may be," etc. [1Peter 1:7.] We certainly dread diseases, and want, and exile, and prison, and reproach, and death, because we regard them as evils; but when we understand that they are turned through God's kindness unto helps and aids to our salvation, it is ingratitude to murmur, and not willingly to submit to be thus paternally dealt with. Paul says, in Romans 5:3, that we are to glory in tribulations; and James says here, that we are to rejoice. "We glory," says Paul, "in tribulations, knowing that tribulation worketh patience." What immediately follows seems contrary to the words of James; for he mentions probation in the third place, as the effect of patience, which is here put first as though it were the cause. But the solution is obvious; the word there has an active, but here a passive meaning. Probation or trial is said by James to produce patience; for were not God to try us, but leave us free from trouble, there would be no patience, which is no other thing than fortitude of mind in bearing evils. But Paul means, that while by enduring we conquer evils, we experience how much God's help avails in necessities; for then the truth of God is as it were in reality manifested to us. Hence it comes that we dare to entertain more hope as to futurity; for the truth of God, known by experience, is more fully believed by us. Hence Paul teaches that by such a probation, that is, by such an experience of divine grace, hope is produced, not that hope then only begins, but that it increases and is confirmed. But both mean, that tribulation is the means by which patience is produced. Moreover, the minds of men are not so formed by nature, that affliction of itself produces patience in them. But Paul and Peter regard not so much the nature of men as the providence of God through which it comes, that the faithful learn patience from troubles; for the ungodly are thereby more and more provoked to madness, as the example of Pharaoh proves. [1]

Footnotes

1 - The word used by James is dochimion, trial, the act of testing, and by Paul dochime, the result of testing, experience. James speaks of probation, and Paul of the experience gained thereby.

Knowing this, that the trying of your faith worketh patience - Patience is one of the fruits of such a trial, and the grace of patience is worth the trial which it may cost to procure it. This is one of the passages which show that James was acquainted with the writings of Paul. See the Introduction, Section 5. The sentiment expressed here is found in Romans 5:3. See the notes at that verse. Paul has carried the sentiment out farther, and shows that tribulation produces other effects than patience. James only asks that patience may have its perfect work, supposing that every Christian grace is implied in this.

The trying of your faith - Trials put religion, and all the graces of which it is composed to proof; the man that stands in such trials gives proof that his religion is sound, and the evidence afforded to his own mind induces him to take courage, bear patiently, and persevere.

(3) Knowing [this], that the (d) trying of your faith worketh patience.
(3) The second, because patience, a surpassing and most excellent virtue, is brought about in us by this means.
(d) That by this your faith is tried, that is, those various temptations.

Knowing this,.... By experience; as everyone that is trained up in the school of affliction does: the apostle appeals to the saints, to whom he writes, for the truth of what he was about to say; and which he gives as a reason why they should rejoice in afflictions, because it is a known fact,
that the trying of your faith worketh patience: two things afflictions do when sanctified; one is, they try faith, the truth of it, and make it appear to be true, genuine, and precious, like gold tried in the fire; see 1-Peter 1:6 and the other is, that they produce patience: saints being inured to afflictions, become by degrees more patient under them; whence it is good for a man to bear the yoke in his youth: this phrase may be understood, both of faith, which being tried by afflictions, produces patience; for where the one is in exercise, the other is also, and both are necessary under afflictive providences; and also of afflictions, which try faith, and being sanctified by the Spirit of God, work patience, which is a fruit of the Spirit; for otherwise the effect of them is impatience; and this agrees with the Apostle Paul in Romans 5:3.

the trying--the testing or proving of your faith, namely, by "divers temptations." Compare Romans 5:3, tribulation worketh patience, and patience experience (in the original dokime, akin to dokimion, "trying," here; there it is experience: here the "trying" or testing, whence experience flows).
patience--The original implies more; persevering endurance and continuance (compare Luke 8:15).