משנה על ברכות 1:2

Negaim may not be inspected in the early morning or in the evening, nor in a house, nor on a cloudy day, because then the dull white appears like bright white; nor may they be inspected at noon, because then the bright white appears like dull white. When are they to be inspected? During the third, fourth, fifth, eighth or ninth hour, the words of Rabbi Meir. Rabbi Judah ruled: during the fourth, fifth, eighth or ninth hour.