Leviticus 15:18

The woman also with whom man shall lie [with] seed of copulation, they shall [both] bathe [themselves] in water, and be unclean until the even.

Ver. 18. With seed of copulation.] Though lawful in itself, as being the ordinance of God. Gen 2:24 Sin is like copperas, a which will turn wine or milk into ink; or leaven, which turns a very passover into pollution.

a A name given from early times to the protosulphates of copper, iron, and zinc (distinguished as blue, green, and white copperas respectively); etymologically it belonged properly to the copper salt; but in English use, when undistinguished by attribute or context, it has always been most commonly, and is now exclusively, applied to green copperas, the proto-sulphate of iron or ferrous sulphate (Fe Son 4:1-16), also called green vitriol, used in dyeing, tanning, and making ink.