The later rabbis, combining this verse with the mystery hanging over the origin and name of David's mother, represent him as born in adultery. (See Stanley, Jewish Church, chap. ii., p. 46, Note.) The word rendered conceived is certainly one generally used of animal desire. (The marginal warm me is erroneous.) But the verse is only a statement of the truth of experience so constantly affirmed in Scripture of hereditary corruption and the innate proneness to sin in every child of man. The argument for a personal origin to the psalm from this verse seems strong; but in Psalm 129:1, and frequently, the community is personified as an individual growing from youth to age, and so may here speak of its far-back idolatrous ancestry as the mother who conceived it in sin.
and in sin did my mother conceive me; by whom cannot be meant Eve; for though she is the mother of all living, and so of David, yet could not, with any propriety, be said to conceive him: this only could be said of his immediate parent, not even of his next grandmother, much less of Eve, at the distance of almost three thousand years. Nor does the sin in which he was conceived intend any sin of his parents, in begetting and conceiving him, being in lawful wedlock; which acts cannot be sinful, since the propagation of the human species by natural generation is a principle of nature implanted by God himself; and is agreeably to the first law of nature, given to man in a state of innocence, "increase and multiply", Genesis 1:28. Marriage is the institution of God in paradise; and in all ages has been accounted "honourable in all, when the bed is undefiled", Hebrews 13:4. Nor does it design his being conceived when his mother was in "profluviis", of which there is no proof, and is a mere imagination, and can answer no purpose; much less that he was conceived in adultery, as the contenders for the purity of human nature broadly intimate; which shows how much they are convicted by this text, to give into such an interpretation of it, at the expense of the character of an innocent person, of whom there is not the least suggestion of this kind in the Holy Scriptures; but on the contrary, she is represented as a religious woman, and David valued himself upon his relation to her as such, Psalm 86:16. Besides, had this been the case, as David would have been a bastard, he would not have been suffered to enter into the congregation of the Lord, according to the law in Deuteronomy 23:2; whereas he often did with great delight, Psalm 42:4. Moreover, it is beside his scope and design to expose the sins of others, much less his own parents, while he is confessing and lamenting his own iniquities: and to what purpose should he mention theirs, especially if he himself was not affected by them, and did not derive a corrupt nature from them? Nor is the sin he speaks of any actual sin of his own, and therefore he does not call it, as before, "my" iniquity and "my" sin; though it was so, he having sinned in Adam, and this being in his nature; but "iniquity" and "sin", it being common to him with all mankind. Hence we learn the earliness of the corruption of nature; it is as soon as man is conceived and shapen; and that it is propagated from one to another by natural generation; and that it is the case of all men: for if this was the case of David, who was born of religious parents, was famous for his early piety, and from whose seed the Messiah sprung, it may well be concluded to be the case of all. And this corruption of nature is the fountain, source, and spring of all sin, secret and open, private and public; and is mentioned here not as an extenuation of David's actual transgressions, but as an aggravation of them; he having been, from his conception and formation, nothing else but a mass of sin, a lump of iniquity; and, in his evangelical repentance for them, he is led to take notice of and mourn over the corruption of his nature, from whence they arose. The Heathens themselves affirm, that no man is born without sin (c).
(c) "Nam vitiis nemo sine nascitur". Horat. Sermon. l. 1. Satyr. 3.