Since external acts are not being depicted here, but the inward irritation of passion, the words "you murder" should not be understood in the narrow, literal sense of bodily murder. In connection with the next word, "you envy," they mean hatred of one's neighbor (cf. 1 Jn 3:15). Such hatred does every evil to him and thereby commits moral murder (cf. Mt 5:21-22).
Envy, or zeal (cf. Jas 3:14), is placed here beside murder. It is a passion that draws a man to do every possible evil to the neighbor who is the object of his envy. Therefore it too is a fratricidal passion.
"One must know that he is not speaking here of bodily murder and enmity. That would be grievous to hear even of robbers, and still more of believers, even if only some, who come to the Lord. It seems to me that he calls murderers those who murder their own souls by undertakings through which they are hostile to piety.
"So further on (Jas 4:4), he calls adulteries and adulterers not those who truly are such in act, but those who sin against the divine commandments by mixing their own inventions with them. No one would endure a teacher who was a fornicator, even if he himself were filthier than swine. Thus he speaks of murders and wars not bodily, but spiritual" (Theophylact).
"And cannot obtain": that is, the very thing for which you murder and envy. Passion again punishes itself and grows still stronger and hotter. It now shows itself in clearer and more direct outward acts: "you quarrel and fight."
These words answer the question, "Where do wars and conflicts among you come from?" (v. 1). The Apostle has clearly traced how these enmities and conflicts arise from desires warring in the members (v. 1).
"And you do not have": the very thing on account of which all this occurs. The passions, or desires, struggle, war, and behave lawlessly. Yet they receive no inward satisfaction and are not pacified. This is an inward moral law, by which passions punish themselves.
"Because you do not ask," that is, in prayer. This does not mean that prayer for the satisfaction of murderous passions could be heard by God and fulfilled by Him. That would contradict the very idea of true prayer.
By this expression the Apostle shows that prayer could be the strongest and most decisive means for pacifying the passions, and therefore for ending enmity and conflict. It would be common prayer of all for all. Yet such prayer is absent among those to whom he speaks.