Biblical Commentary on the Old Testament, by Carl Friedrich Keil and Franz Delitzsh, [1857-78], at sacred-texts.com
The Uncleanness of Secretions. - These include (1) a running issue from a man (Lev 15:2-15); (2) involuntary emission of seed (Lev 15:16, Lev 15:17), and the emission of seed in sexual intercourse (Lev 15:18); (3) the monthly period of a woman (Lev 15:19-24); (4) a diseased issue of blood from a woman (Lev 15:25-30). They consist, therefore, of two diseased and two natural secretions from the organs of generation.
The running issue from a man is not described with sufficient clearness for us to be able to determine with certainty what disease is referred to: "if a man becomes flowing out of his flesh, he is unclean in his flux." That even here the term flesh is not a euphemism for the organ of generation, as is frequently assumed, is evident from Lev 15:13, "he shall wash his clothes and bathe his flesh in water," when compared with Lev 16:23-24, Lev 16:28, etc., where flesh cannot possibly have any such meaning. The "flesh" is the body as in Lev 15:7, "whoever touches the flesh of him that hath the issue," as compared with Lev 15:19, "whosoever toucheth her." At the same time, the agreement between the law relating to the man with an issue and that concerning the woman with an issue (Lev 15:19, "her issue in her flesh") points unmistakeably to a secretion from the sexual organs. Only the seat of the disease is not more closely defined. The issue of the man is not a hemorrhoidal disease, for nothing is said about a flow of blood; still less is it a syphilitic suppuration (gonorrhaea virulenta), for the occurrence of this at all in antiquity is very questionable; but it is either a diseased flow of semen (gonorrhaea), i.e., an involuntary flow drop by drop arising from weakness of the organ, as Jerome and the Rabbins assume, or more probably, simply blenorrhaea urethrae, a discharge of mucus arising from a catarrhal affection of the mucous membrane of the urethra (urethritis). The participle זב יהיה is expressive of continued duration. In Lev 15:3 the uncleanness is still more closely defined: "whether his flesh run with his issue, or his flesh closes before his issue," i.e., whether the member lets the matter flow out or by closing retains it, "it is his uncleanness," i.e., in the latter case as well as the former it is uncleanness to him, he is unclean. For the "closing" is only a temporary obstruction, brought about by some particular circumstance.
Every bed upon which he lay, and everything upon which he sat, was defiled in consequence; also every one who touched his bed (Lev 15:5), or sat upon it (Lev 15:6), or touched his flesh, i.e., his body (Lev 15:7), was unclean, and had to bathe himself and wash his clothes in consequence.
The conveyance in which such a man rode was also unclean, as well as everything under him; and whoever touched them was defiled till the evening, and the person who carried them was to wash his clothes and bathe himself.
This also applied to every one whom the man with an issue might touch, without first rinsing his hands in water.
Vessels that he had touched were to be broken to pieces if they were of earthenware, and rinsed with water if they were of wood, for the reasons explained in Lev 11:33 and Lev 6:21.
When he was cleansed, i.e., recovered from his issue, he was to wait seven days with regard to his purification, and then wash his clothes and bathe his body in fresh water, and be clean. On the eighth day he was to bring two turtle-doves or young pigeons, in order that the priest might prepare one as a sin-offering and the other as a burnt-offering, and make an atonement for him before the Lord for his issue.
Involuntary emission of seed. - This defiled for the whole of the day, not only the man himself, but any garment or skin upon which any of it had come, and required for purification that the whole body should be bathed, and the polluted things washed.
Sexual connection. "If a man lie with a woman with the emission of seed, both shall be unclean till the evening, and bathe themselves in water." Consequently it was not the concubitus as such which defiled, as many erroneously suppose, but the emission of seed in the coitus. This explains the law and custom, of abstaining from conjugal intercourse during the preparation for acts of divine worship, or the performance of the same (Exo 19:5; Sa1 21:5-6; Sa2 11:4), in which many other nations resembled the Israelites. (For proofs see Leyrer's article in Herzog's Cyclopaedia, and Knobel in loco, though the latter is wrong in supposing that conjugal intercourse itself defiled.)
The menses of a woman. - "If a woman have an issue, (if) blood is her issue in her flesh, she shall be seven days in her uncleanness." As the discharge does not last as a rule more than four or five days, the period of seven days was fixed on account of the significance of the number seven. In this condition she rendered every one who touched her unclean (Lev 15:19), everything upon which she lay or sat (Lev 15:20), every one who touched her bed or whatever she sat upon (Lev 15:21, Lev 15:22), also any one who touched the blood upon her bed or seat (Lev 15:23, where הוּא and בּו are to be referred to דּם); and they remained unclean till the evening, when they had to wash their clothes and bathe themselves.
If a man lay with her and her uncleanness came upon him, he became unclean for seven days, and the bed upon which he lay became unclean as well. The meaning cannot be merely if he lie upon the same bed with her, but if he have conjugal intercourse, as is evident from Lev 20:18 and Num 5:13 (cf. Gen 26:10; Gen 34:2; Gen 35:22; Sa1 2:22). It cannot be adduced as an objection to this explanation, which is the only admissible one, that according to Lev 18:19 and Lev 20:18 intercourse with a woman during her menses was an accursed crime, to be punished by extermination. For the law in Lev 20:18 refers partly to conjugal intercourse during the hemorrhage of a woman after child-birth, as the similarity of the words in Lev 20:18 and Lev 12:7 (דּמיה מקור) clearly proves, and to the case of a man attempting cohabitation with a woman during her menstruation. The verse before us, on the contrary, refers simply to the possibility of menstruation commencing during the act of conjugal intercourse, when the man would be involuntarily defiled through the unexpected uncleanness of the woman.
Diseased issue from a woman. - If an issue of blood in a woman flowed many days away from (not in) the time of her monthly uncleanness, or if it flowed beyond her monthly uncleanness, she was to be unclean as long as her unclean issue continued, just as in the days of her monthly uncleanness, and she defiled her couch as well as everything upon which she sat, as in the other case, also every one who touched either her or these things.
After the issue had ceased, she was to purify herself like the man with an issue, as described in Lev 15:13-15. - Obedience to these commands is urged in Lev 15:31 : "Cause that the children of Israel free themselves from their uncleanness, that they die not through their uncleanness, by defiling My dwelling in the midst of them." הזּיר, Hiphil, to cause that a person keeps aloof from anything, or loosens himself from it, from נזר, Niphal to separate one's self, signifies here deliverance from the state of uncleanness, purification from it. Continuance in it was followed by death, not merely in the particular instance in which an unclean man ventured to enter the sanctuary, but as a general fact, because uncleanness as irreconcilable with the calling of Israel to be a holy nation, in the midst of which Jehovah the Holy One had His dwelling-place (Lev 11:44), and continuance in uncleanness without the prescribed purification was a disregard of the holiness of Jehovah, and involved rebellion against Him and His ordinances of grace.
Concluding formula. The words, "him that lieth with her that is unclean," are more general than the expression, "lie with her," in Lev 15:24, and involve not only intercourse with an unclean woman, but lying by her side upon one and the same bed.