Mishná sobre Negaim 2:7

Rabbi Hanina, the vice-chief of priests, says: the colors of negaim are sixteen. Rabbi Dosa ben Harkinas says: the colors of negaim are thirty-six. Akaviah ben Mahalalel says: seventy-two. Rabbi Hanina the vice-chief of priests says: negaim may not be inspected for the first time at the end of Shabbat, since the end of that week will fall on Shabbat; Nor on a Monday, since the end of the second week will fall on Shabbat; Nor on a Tuesday, in the case of houses, since the end of the third week will fall on Shabbat. Rabbi Akiva says: they may be inspected at all times, and if the time for the second inspection falls on Shabbat it is postponed to after Shabbat; and this procedure leads sometimes to a leniency and sometimes to a stringency.

Everyone can become impure from negaim, except for a non-Jew and a resident alien. All are qualified to inspect negaim, but only a priest may declare them unclean or clean. He is told, "Say: 'unclean,'" and he repeats "unclean," or "Say: 'clean,'" and he repeats "clean." Two negaim may not be inspected simultaneously whether in one man or in two men; rather he inspects one first and isolates him, certifies him as unclean or pronounces him clean, and then he inspects the second. One who is isolated may not be isolated again nor may one who is certified unclean be certified unclean again. One who is certified unclean may not be isolated nor may one who is isolated be certified unclean. But in the beginning, or at the end of a week, he may isolate on account of the one nega and isolate him on account of another one; he may certify him unclean on account of one sign and also certify him unclean on account of another sign; he may isolated the one sign and declare the other clean, or certify the one unclean and declare the other clean.

There are [laws] that apply to white hair that do not apply to quick flesh, while others apply to quick flesh and not to white hair. White hair causes uncleanness in a boil and in a burn, whether growing together or dispersed, and whether encompassed or unencompassed. There are [laws] that apply to quick flesh, for quick flesh causes uncleanness in scalp baldness and in forehead baldness, whether it was turned or was not turned, it prevents the cleanness of one who is turned all white, and causes uncleanness whatever its color, and these do not apply to white hair.

If the two hairs were black at the root and white at the tip he is clean. If they were white at the root and black at the tip he is unclean. How much whiteness must there be? Rabbi Meir says: any amount. Rabbi Shimon says: enough to be cut with a pair of scissors. If it was single at the root but split at the tip, and it looks like two hairs, he is clean. If a bright spot had [two] white hairs or black hair he is unclean, for we are not concerned that the place of the black hair lessened the space of the bright spot, since the former is of no consequence.

One who touches the upper beam, the lower beam, the harnesses, the sley, the thread that is drawn over purple material, or a spool which is not to be shot back, remains clean. If he touches the woof, the standing warp, the double thread that is drawn over purple material or a spool which is to be shot back, he becomes unclean. If one touches the wool that is on the distaff, or on the spool, he remains clean. If he touches the spinner: Before it was uncovered he is unclean, After it was uncovered he remains clean.