What is the minimum size of michyah (healthy flesh) required to serve as a sign of impurity?
Halacha 1 specifies that michyah must be at least the size of a lentil when a square is imposed upon it — which equals four hairs two lengthwise and two widthwise.
Question 2
A baheret has healthy flesh scattered in two mustard-seed spots in its center. Can they combine to form a lentil?
Halacha 1 explicitly states that scattered healthy flesh — even if both pieces are in the center of the baheret — cannot be combined to form a lentil. It must be in one contiguous location.
Question 3
Does michyah require the baheret to have preceded it in order to be a sign of impurity?
Halacha 4 explains that michyah is always a sign of impurity whether it preceded the baheret or the baheret preceded it, because the Torah did not use the phrase 'and it turned' in connection with michyah (unlike white hair).
Question 4
A baheret is exactly a gris in size with michyah exactly a lentil in size in its center. What happens if the michyah grows?
Halacha 5 states that if the michyah grows such that the baheret can no longer maintain a two-hair margin around it, the person becomes pure — the positional requirement is no longer met.
Question 5
Why does michyah at the tip of a finger not render a person impure when it is inside a baheret?
Halacha 8 explains that at the tips of 24 curved limbs, the michyah divides the blemish — part flows down one side, part down the other — so the priest cannot see the entire blemish as a single entity as required by Leviticus 13:5.