הלכות טומאת צרעת

Flesh that heals is not considered as a sign of impurity unless it is the size of a lentil when a square is imposed upon it or more. How large is that? Enough for four hairs to grow, two lengthwise and two widthwise. The flesh that heals must be in the center of the baheret and the baheret must surround it on all sides with there being a margin of the size of two hairs or more between the healthy flesh and the edge of the baheret. If, however, the healthy flesh is at the side of the baheret, it is not a sign of impurity.
If the healthy flesh was scattered in different places in the baheret, e.g., there was healthy flesh the size of a mustard seed in one place and healthy flesh the size of a mustard seed in another place, they are not combined to be considered as the size of a lentil even though they are both in the midst of the same baheret. Instead, there must be healthy flesh the size of a lentil when a square is imposed upon it or more in one place in the midst of the baheret.

Flesh that healed is not a sign of impurity unless it is in the baheret itself.
What is implied? In the midst of a baheret, there was a boil, burnt flesh, or a healed boil or burnt flesh, or a bohak and there was totally healthy flesh in the midst of these abnormal skin features. Even though the healthy flesh is in the midst of the baheret, it is not a sign of impurity, because it is within the boil, the burnt flesh, the bohak, or their healed flesh. Similarly, if a boil or its healed flesh, burnt flesh or its healed flesh, or a bohak surrounds the healthy flesh, or one of these abnormal skin features is directly next to the healthy flesh at its side, or one of these abnormal skin features divides the healthy flesh and enters within it, it is not a sign of impurity. This is like a baheret that does not have any sign of impurity and the person should be isolated.
If the boil, the burnt flesh, or the bohak in which the healthy flesh was found, that was at its side, that surrounded it, or that entered it disappeared and thus the healthy flesh alone was found within the baheret at the end of the first week or at the end of the second week, the person should be deemed definitively impure. If they did not depart, he should be released from the process of inspection.

Healthy flesh is always a sign of impurity, whether the healthy flesh existed before the baheret or the baheret existed before the healthy flesh, because concerning it, the Torah does not state: "And it turned." Although the Torah does state Leviticus 13:10: "And it turned hair to white and there was healthy flesh in the si'ait," there is no need for a blemish to have both white hair and healthy flesh. Instead, each one independently is a sign of impurity. They were mentioned together only to identify the measure of healthy flesh that imparts impurity: enough to contain enough white hair to cause a person to be deemed impure, i.e., two hairs.

When a baheret is exactly the size of a gris and, in its midst, there is healthy flesh exactly the size of a lentil, the afflicted person should be deemed definitively impure. If the size of the baheret or the size of the healthy flesh was diminished, he is pure. Similarly, if the size of the healthy flesh in this baheret increased, he is pure. The rationale is that a baheret does not impart impurity because of healthy flesh until it has a margin of afflicted flesh the width of two hairs on every side.
If the healthy flesh was less than a lentil and then it increased until it reached the size of a lentil, the afflicted person should be deemed definitively impure. If the size of the healthy flesh then diminished or disappeared, its status returns to its initial state and there is no sign of impurity.

If a baheret is larger than a gris and it contains healthy flesh that is larger than a lentil, the afflicted person is impure whether they increase or decrease in size, provided the size of the baheret does not decrease to less than a gris, the size of the healthy flesh does not decrease to less than a lentil, and the healthy flesh does not come within two hairsbreadth of the edge of the baheret, as we explained.

When the baheret is the size of gris and there is healthy flesh the size of a lentil or more surrounding it from the outside and a second baheret surrounding the healthy flesh, the inner baheret would cause the afflicted person to be isolated, for it does not have a sign of impurity. The outer baheret causes him to be deemed definitively impure, because there is healthy flesh in its midst.
If the healthy flesh that was between the two blemishes was diminished or disappeared entirely - whether it was diminished or reduced from the inside or was diminished from the outside, the two are considered as one baheret that does not have a sign of impurity.

When a baheret is located at the tip of one of the limbs and there is healthy flesh in its midst at the tip, it is not considered as a sign of impurity, because the healthy flesh divides the blemish into two. Thus one portion streams down one side of the limb and another portion streams down the other. The person is thus not deemed impure, because Leviticus 13:5 states: "And the priest shall see it." Implied is that he shall see the entire blemish as a single entity.
These are the 24 tips of the limbs that do not impart impurity when healthy flesh is found upon them: the tips of the fingers and the toes, the tips of the ear and the nose, the tip of the corona of the male organ, and the tips of a woman's breasts. The tips of a man's breasts, warts, and blisters, by contrast, impart impurity if there is a baheret and healthy flesh upon them.

When there was a flat surface the size of a gris at the tip of any of these limbs, a blemish imparts impurity. If they were round as is the case for most people, blemishes are pure.
What is implied? If there is a baheret the size of a gris at the tip of one's nose or the tip of one's finger, descending to either direction, he is pure, as implied by the phrase: "And the priest shall see it." Implied is that he shall see the entire blemish as a single entity.