Albert Barnes Commentary Leviticus 15:24

"And if any man lie with her, and her impurity be upon him, he shall be unclean seven days; and every bed whereon he lieth shall be unclean." — Leviticus 15:24 (ASV)

This must refer to an unexpected occurrence. Intercourse during the acknowledged period was a heavy crime, and was to be punished by “cutting off” (Leviticus 18:19; Leviticus 20:18; Ezekiel 18:6).