This verse is not only difficult to find in another scripture, it is also a bit difficult to understand. However, in studying it, I am convinced that a fully understanding of the meaning in context is the key to finding the source of the quote. So, we will start with interpretation.
The quotation itself is made up of three parts. First, the subject of the sentence is the "spirit that dwelleth in us." Second, the verb or action of this "spirit" is that it "lusteth." Third, the object or the result of this action is "to envy." Each of these parts must be understood in order to understand the whole.
The Bible often uses the word, spirit, to indicate the inner part of man that receives the life of God and is enabled by God's Spirit. We are taught by the Spirit through our spirit (1 Corinthians 2:11-14) and the Spirit of God bears witness to our spirit (Romans 8:16). However, the word can be used in other ways as well; as this passage shows. The "spirit" of James 4:5 is a spirit that lusts. It is therefore our earthly life and not our heavenly one. It is the "spirit of the world" (1 Corinthians 2:12) and not the life from above.
To lust means to wrongly desire something for the sake of self-gratification. James 4:1-5 uses some form of the word, lust, four times. Fightings come from "your lusts that war in your members" (James 4:1). To "lust" is to "desire to have" (James 4:2). When you pray, you ask for things "that ye may consume it upon your lusts" (James 4:3). And, finally, the natural human spirit "lusteth to envy" (James 4:5). This passage strongly deals with this sinful motivation.
We are then told that this natural lust leads "to envy." Envy is defined as a feeling of displeasure and ill will because someone else has advantages that you do not possess. Envy is connected to the wisdom of this world at the end of the previous chapter. You are not to glory if you have "bitter envying and strife in your hearts" (James 3:14). The wisdom that leads to such envy is worldly and "where envying and strife is, there is confusion and every evil work" (James 3:16). James 4:4 warns of the danger of making "friendship of the world." If we love the world, we will eventually envy those who have the things of this world.
The teaching is clear. If I follow the wisdom of this world and allow the natural lusts in my human heart to control me, I will be filled with envy toward those I see as having what I desire to have. Envy then expresses itself in strife (James 3:14, 16) and further leads to "confusion and every evil work" (James 3:16).
We can see the power of this statement but that does not solve the original problem. This statement is introduced with this phrase: "Do ye think that the scripture saith in vain?" Yet, with careful research and allowing for the fact that God does not always quote Himself word for word, Bible scholars have not been able to pin down the quotation in either Old or New Testament scriptures. What is the answer?
We must consider the probability that the phrase, "scripture saith," does not refer to a word for word or even an approximate quotation. But what else is a possibility? The verb, saith, is a form of the verb, say. In the dictionary, we find that to say has several meanings. Consider the following meanings. To say can mean to indicate or show, as in "the clock says four." It can mean to allege or report, as in "people say he's smart." It can also mean to communicate an idea, as in "what does that picture say to you?" Therefore, to say that the scripture says can have more than one meaning. Since we can eliminate the phrase in James 4:5 as being a reference to a direct quote, we can safely conclude that James is using the words in one of the alternative ways. Do not the scriptures teach us that the lusts our heart lead us to the sin of envy? That is the import of what James has said.
What scriptures then teach (or say) this? Well, the danger of looking at what others have (lusting) and allowing this to become envy is in numerous passages. Consider the following:
Psalm 37:1 Fret not thyself because of evildoers, neither be thou envious against the workers of iniquity.
Psalm 73:3 For I was envious at the foolish, when I saw the prosperity of the wicked.
Proverbs 23:17 Let not thine heart envy sinners: but be thou in the fear of the LORD all the day long.
Proverbs 24:1 Be not thou envious against evil men, neither desire to be with them.
Proverbs 24:19 Fret not thyself because of evil men, neither be thou envious at the wicked;
- Ecclesiastes 4:4 Again, I considered all travail, and every right work, that for this a man is envied of his neighbour. This is also vanity and vexation of spirit.
What the scripture says about the danger of envy and how the heart tends to it is not to be found in one verse of the Old Testament. It is rather to be found in the distilled teaching of numerous passages. James is teaching us that scripture does not only say things through exact quotations, but it also speaks though truth found by joining multiplied scriptures together. That, in itself, is an important lesson.