Albert Barnes Commentary Leviticus 13:5

"and the priest shall look on him the seventh day: and, behold, if in his eyes the plague be at a stay, and the plague be not spread in the skin, then the priest shall shut him up seven days more:" — Leviticus 13:5 (ASV)

And the plague spread not – Rather, it did not advance, showing that the disease is under the cuticle and taking on the symptoms of (Leviticus 13:3).