Albert Barnes Commentary Leviticus 15:13

"And when he that hath an issue is cleansed of his issue, then he shall number to himself seven days for his cleansing, and wash his clothes; and he shall bathe his flesh in running water, and shall be clean." — Leviticus 15:13 (ASV)

The mere cessation of the discharge does not make him clean: he must wait seven days, and so forth, preparatory to his offering sacrifice.