This is the law of the plague of leprosy in a garment. Leviticus 13:59
Trivia: How long is a mother unclean after delivering a baby girl?
"Corn" is obviously a mistranslation in the King James Version, since there was no corn in Egypt or anywhere in the Eastern hemisphere in biblical times.
Corn was domesticated 10,000 years ago by indigenous peoples in what is now Mexico.
See notes: Gen 41:49, Lev 2:14