James wants his readers to stop looking outside themselves for the cause of their quarrels. His first question asks where the fighting comes from. His second answers it with a question they cannot deny: it comes from desires at war inside them. Gill says these were not "public and national wars," and he judges it best to read them as strifes and quarrels about honours and riches. He pictures the lusts (pride, envy, covetousness, ambition) as soldiers "stationed and quartered in the members," and adds, "from this inward war arise external ones." Matthew Henry's Concise Commentary sums it up: "all wars and fightings come from the corruptions of our own hearts."

James answers in the second half of the verse and then traces the path from desire to conflict: "Ye lust, and have not: ye kill, and desire to have, and cannot obtain: ye fight and war, yet ye have not, because ye ask not" (James 4:2). Even their prayers were bent: "Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts" (James 4:3). He then calls them back to God: "Submit yourselves therefore to God" (James 4:7).

"Lusts" in the KJV is broader than sexual desire; it means strong cravings of any kind, which the ESV calls "passions." "Members" means the parts of the body. Barnes thinks the more probable reference is to the strifes of sects and parties among the Jewish people of that day rather than to the Jewish seditions that later broke out against Rome, though he notes that the same "corrupt passions of men have made the earth one great battle-field." He compares Paul's words about "another law in my members, warring against the law of my mind" (Romans 7:23) and "the flesh lusteth against the Spirit" (Galatians 5:17).

This question goes to the root. Commentators differ on who was fighting. Barnes thinks James means strifes "among the Jewish people," which Christian converts were "in great danger of participating" in, while Gill reads them as quarrels among the Christians James wrote to, "about honours and riches." Either way, the fights among them were not mainly about circumstances or difficult people; they grew from unmet desires inside. Matthew Henry's Concise Commentary notes that "Sinful desires and affections stop prayer," and James 4:2-3 shows exactly that: they did not ask, or they asked only to feed their desires.

But James does not leave them stuck in the war. The same passage holds out God's answer: "he giveth more grace," and "giveth grace unto the humble" (James 4:6). "Draw nigh to God, and he will draw nigh to you" (James 4:8). Peace between people begins with surrender to God.