verses 16-17
Lev 15:16-17Involuntary 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.
Verse 18
Lev 15:18Sexual 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; 1Sa 21:5-6; 2Sa 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.)
verses 19-23
Lev 15:19-23The 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.
Verse 24
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; 1Sa 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
