3:1 Not many of you should presume to be teachers [apparently many Jewish Christians wanted to teach (though they lacked the maturity and/or giftedness to do so); teachers played an important role in the early church (cf. 1 Cor. 12:28; Eph. 4:11); some wanted to be teachers because they desired the status, respect, and authority that came with the position; not all who want to be teachers have the spiritual gift of teaching; unfit teachers can be as harmful as false teachers], my brothers, because you know that we [James included himself] who teach will be judged more strictly [legal term that refers to a greater sentence from a judge].
Note: What is the danger of recruiting individuals to teach too quickly after their conversion?
3:2 [James turned his attention to speech, the primary means of communication for teachers] We all [everyone, not just teachers] stumble [used figuratively here: means “to commit sin”] in many ways. If anyone is never at fault in what he says, he is a perfect [complete or mature] man, able to keep his whole body in check [does not allow his body to become instrument of sin].
by Philip Burroughs Strong
“The boneless tongue, so small and weak,
Can crush and kill,” declares the Greek.
“The tongue destroys a greater horde,”
The Turk asserts, “than does the sword.”
A Persian proverb wisely saith,
“A lengthy tongue—an early death”;
Or sometimes takes this form instead,
“Don’t let your tongue cut off your head.”
“The tongue can speak a word whose speed,”
Says the Chinese, “outstrips the steed”;
While Arab sages this impart,
“The tongue’s great storehouse is the heart.”
From Hebrew wit the maxim sprung,
“Though feet should slip, ne’er let the tongue.”
The sacred writer crowns the whole,
“Who keeps his tongue doth keep his soul.”
3:3 [James used three illustrations from daily life to illustrate that the effectiveness of the instrument, not its size, is most important] When we put  bits [small piece of metal with reins attached] into the mouths of horses to make them obey us, we can turn the whole animal [illustrates how a small thing has influence over something much larger].
3:4 Or take ships as an example. Although they are so large and are driven by strong winds, they are steered by a very small  rudder wherever the pilot wants to go.
3:5 Likewise the tongue is a small part of the body, but it makes great boasts [arrogant bragging or talking big]. Consider what a great forest is set on fire by a small  spark.
3:6 The tongue also is a fire [and therefore has the potential for great destruction; an uncontrolled tongue can destroy relationships, reputations, and churches], a world of [all kinds of] evil among the parts of the body. It [the destructive use of speech] corrupts [spots, stains, defiles] the whole person, sets the whole course of his life [all of life from birth to death] on fire, and is itself set on fire by hell [“Gehenna” is Gr. form of Heb. name of Valley of Hinnom (place near Jerusalem where people burned their trash); Gehenna a symbol for eternal fire and final judgment (Mk. 9:43,47); cf. Matt. 5:22].
3:7 All kinds of animals, birds, reptiles and creatures of the sea are being tamed and have been tamed by man [emphasizes humanity’s control over animal world],
3:8 but [in contrast to the taming of various kinds of animals] no man [however, the indwelling Holy Spirit can help people gain control of their tongues] can tame [to subdue or conquer] the tongue. It is a restless [unruly and unrestrainable; like an animal pacing back and forth in a cage] evil, full of deadly poison [like a deadly snake].
3:9 With the tongue we praise [our Eng. Word “eulogy”: to offer good words or to speak well of someone; represents the highest use of the tongue] our Lord and Father, and with it [the same tongue] we curse [to invoke evil] men, who have been made in God’s likeness.
3:10 Out of the same mouth [Spurgeon said “What lies in the well of the heart comes up in the bucket of speech.”; cf. Mk. 7:15,20-23] come praise and cursing. My brothers [James was addressing Christians], this should not be [it is inappropriate or incongruous].
3:11 Can both fresh [literally “sweet” or good for drinking] water and salt [literally “bitter” or unfit for drinking] water flow [refers to “gushing forth” or “bubbling up”] from the same spring [rhetorical question with negative answer]?
3:12 My brothers, [James turned to an agricultural metaphor to reinforce his point about inconsistent speech] can a fig tree bear olives, or a grapevine bear figs? [the answer is “no”] Neither can a salt spring produce fresh water.
3:13 Who is wise and understanding among you [James answered this question in the next phrase]? Let him show it by his good life [cf. Matt. 6:19-21,33], by deeds done in the humility that comes from wisdom.
3:14 But if you harbor bitter envy [anger at the accomplishments and successes of others] and selfish ambition [cf. Phil. 2:3] in your hearts, do not boast about it or deny the truth [the truth that we are harboring bitter envy and selfish ambition].
3:15 Such “wisdom” does not come down from heaven but is earthly, unspiritual, of the devil .
3:16 For where you have envy and selfish ambition, there you find disorder and every evil practice.
3:17 But the wisdom that comes from heaven [literally “from above”] is first of all [means “first in rank”] pure [means “holy” or “separate”]; then peace-loving [cf. Matt. 5:9], considerate [patient, reasonable, fair in dealing with others], submissive [compliant and approachable, willing to yield (as long as no serious moral or doctrinal issue is at stake)], full of mercy [compassion shown toward the needy] and good fruit [probably kind, helpful actions on behalf of needy], impartial [cf. Jas. 2:1] and sincere [to be sincere or without double-mindedness or hypocrisy].
3:18 Peacemakers [those who love and try to promote peace; cf. Matt. 5:9] who sow in peace raise a harvest of righteousness [conduct that pleases God; actions that conform to God’s will].