Who was Cain?
In Genesis 4:1-24 Cain is the first son of Adam and Eve. His birth is hailed as a manifestation of Yahweh's help.
He becomes "a tiller of the ground," and brings to Yahweh an offering of the produce of the soil, his brother Abel, the shepherd, bringing at the same time the fat of the first-born of his own flock.
From Cain and from his offering Yahweh withholds the sign of acceptance which he grants to Abel. That the ground of this difference of treatment is to be found (so Heb 11:4) in Cain's lack of right disposition toward Yahweh is shown by his behavior.
Instead of humbling himself he gives signs of strong indignation at Yahweh's refusal to favor him. Under the just rebuke of Yahweh he hardens his heart and is further confirmed in impenitence. His jealousy of Abel, unrepented of, increases until it culminates in deliberate murder.
Deliberate, for in Gen 4:8 we must restore a clause to the Hebrew text, all the ancient versions bearing witness, and read "And Cain said unto Abel his brother, Let us go into the field," etc. In the vain attempt to conceal his crime Cain adds falsehood to his other sins. He is cursed "from," i.e. away from, that soil upon which he poured out his brother's blood, and must become a fugitive and a wanderer, far from the immediate presence of Yahweh.
Although his remonstrance against the severity of his sentence displays no genuine contrition, still Yahweh in pity appoints a "sign" for his protection. Cain takes up his abode in the land of Nod ("wandering"), and there builds a city and becomes the ancestor of a line which includes Jabal, forefather of tent-dwelling cattle-keepers; Jubal, forefather of musicians; Tubal-cain, forefather of smiths; and Lamech, like Cain, a man of violence.
In Cain's character we see "a terrible outburst of selfwill, pride, and jealousy, leading to a total and relentless renunciation of all human ties and affection." "Among the lessons or truths which the narrative teaches may be instanced: the nature of temptation, and the manner in which it should be resisted; the consequences to which an unsubdued temper may lead a man; the gradual steps by which in the end a deadly crime may be committed; the need of sincerity of purpose lest our offering should be rejected; God's care for the guilty sinner after he has been punished; the interdependence upon one another of members of the human race; and the duties and obligations which we all owe to each other" (Driver). In Heb 11:4 Cain's spiritual deficiency is pointed out; 1 Jn 3:12 observes his envy and jealousy, as "of the wicked one," and Jude 1:11 makes him a very type of the ungodly.
With few and bold strokes the story of Cain as it stands paints for us the character of the first of murderers and the scene of his detection and condemnation. To the religious purpose of the narrative all other things are made tributary.
But if we can not refrain from putting the familiar question, Who was Cain's wife? it is aIso impossible upon close study of Gen 4, as it stands, to avoid asking what was the nature of the sign of Yahweh's acceptance (verse 4), or of the "sign" appointed for Cain (verse 15); or what we are to think of the introduction in the midst of the narrative, without explanation, of such important institutions as sacrifice (verses 3,4) and blood-revenge (verse 14); who were the persons of whom Cain stood in fear (verse 14); who inhabited the city he built (verse 17); how the wanderer and fugitive could become the city-builder; and why the shepherd life should be represented as beginning with Abel (verse 2) and again with Jabal (verse 20); also whether the narrator means that not only the collection of men in cities (verse 17), but also animal husbandry, music and metal-working (verse 20-22) are to be looked upon with disfavor as having sprung from Cain or from his descendants?
Most of these questions find their answers in one consideration: the narrative is not exhaustively complete and is not intended to be so. That a large body of racial traditions existed, from which, with the severest condensation, the author of Gen selected his material, is the conclusion forced by close examination of the Gen narrative and comparison of it with the most ancient extant traditions. "In Gen 4 these old stories are not told for their own sakes. The incompleteness and the difficulties left unsolved do not allow this assumption to be made. They form simply the material foundation, to which higher ideas and doctrines are attached" (Dillmann).
Without going outside the Scripture text we may find strong evidence that the narrative under consideration is founded in part upon ancient sources. Let the line of Cain (Gen 4:17-24) be compared with that of Seth (Gen 5:1-29):
The Hebrew forms of the names show even more clearly that Cain = Kenan, Irad = Jared, Methushael = Methuselah; a single transposition, that of the first and third names after Cain, brings the two Enochs together, and likewise the similar names Mehujael and Mahalalel. Thus we have six names nearly or quite identical; seven ancestors in one list and ten in the other, ending in both cases with a branching into three important characters. Resemblances equally certain, though not by any means so obvious, exist between the names in this double list and the names of the ten kings of Babylonia who reigned before the Flood, as the latter are given by Berosus, the Babylonian historian of the 3rd century BC (see Skinner, Driver, Sayce as below).
Thus one source of which the author in Gen 4 made use appears to have been an ancient list in genealogical form, by which the first of mankind was linked with the beginnings of civilized institutions and articles Another part of his material was the story of a brother's murder of a brother (4:1-16). Many maintain at this point that the narrative must be based upon the doings of tribes, rather than of individuals.
It is true that not seldom in the Old Testament tribal history is related under individual names (compare Gen 49;, Jgs 1, and the tables of tribes in Gen 25:1-4; 36); yet the tribe referred to can hardly be the Kenites of the Old Testament, who appear as the close allies of Israel, not especially bloodthirsty or revengeful, and haunted by no shadow of early crime against a brother tribe.
The indications in Gen 4:1-16 of a developed state of society and a considerable population may go to show that the narrative of the murder was not originally associated with the sons of the first man. Thus there is room to suppose that in the process of condensation and arrangement Cain, son of Adam; Cain, the murderer; and Cain, city-builder and head of a line of patriarchs, have been made one.
The critical conclusions here epitomized are indeed reached by a delicate and difficult process; but it is asserted in their favor that they make possible the removal of difficulties which could be explained in no other manner. The question which will arise with many, What theory of inspiration can be held consistently with the application of such critical processes? is dealt with at length by most modern commentators.
IBSE, "Cain" (in the public domain) with minor edits.