And Adam knew Eve his wife; and she conceived, and bore Cain, and said, I have gotten a man from the LORD.
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Augustine of Hippo
AD 430
Cain was followed by Abel, who was killed by his brother and served as the first prophetic symbol of the . He was like an alien on earth, destined to suffer cruel persecutions at the hands of the wicked men who can properly be called natives of earth because they love this world as their home and find their happiness in the worldly felicity of the earthly city.
Note that the name Cain means “ownership,” which explains what was said at the time of his birth by his father or mother: “I have come into possession of a man through God.”
Through God. Hebrew may signify also "even God "as if she thought this was the promised seed, who, as Onkelos paraphrases it, would serve the Lord. (Calmet)
So little could she foresee the future conduct of Cain, whose name may be derived either from kone, possession and acquisition, or from kun, lamentation. The latter interpretation would have been better verified by the event, and the name of Abel, vanity, or sorrow, for which his parents allege no reason, might also have been reversed, on account of his justice, for which he is canonized by Christ himself, and declared the Just. Pious and significant names were imposed by either parent. Cain was the second man. He was not conceived till after the fall, and was therefore the first born in original sin. (Haydock)
After his disobedience, after their loss of the garden, then it was that the practice of intercourse had its beginning. You see, before their disobedience they followed a life like that of angels, and there was not mention of intercourse.
"Now, Adam had intercourse with his wife Eve." Consider when this happened. After their disobedience, after their loss of the garden, then it was that the practice of intercourse had its beginning. You see, before their disobedience they followed a life like that of the angels, and there was no mention of intercourse. How could there be, when they were not subject to the needs of the body? So, at the outset and from the beginning the practice of virginity was in force, but when through their indifference disobedience came on the scene and the ways of sin were opened, virginity took its leave for the reason that they had proved unworthy of such a degree of good things, and in its place the practice of intercourse took over for the future. Accordingly, consider, I ask you, dearly beloved, how great the esteem of virginity, how elevated and important a thing it is, surpassing human nature and requiring assistance from on high. I mean, for proof that those who practice virginity with enthu...
Since Adam had been blinded in the eyes of his soul and had fallen from the life imperishable, he began to look with his physical eyes. He turned the vision of his eyes on visible objects with affectionate desire and “knew Eve his wife, and she conceived and bore Cain.” Such knowledge is in reality ignorance of all goodness, for had he not first fallen from the knowledge and contemplation of God he would not have been brought down to this knowledge.
