(Leviticus 13:1-2:) "And the LORD spoke unto Moses and unto Aaron, saying: When a man shall have in the skin of his flesh etc." This is what is written (Job 38:25): "Who has split a channel for the flood (shetef)?" Said Rabbi Yehoshua of Sikhnin in the name of Rabbi Levi: In Arabia they call hair (se'ar) shitfa — for every single hair upon a person, He created for it its own well, by itself. Because Job protested and said (Job 9:17): "He who would crush me with a tempest (bisarah) [and multiply my wounds for no cause]" — for no cause He has brought all these sufferings upon me. Elihu said to him: Heaven forbid! (Job 34:10) "Far be it from God to do wickedness, and from the Almighty to do wrong." Rather (Job 34:11): "For according to a man's deeds He repays him, [and according to a man's ways He requites him]" — everything He brings by measure. Said Rabbi Avin the Levite in the name of Rabbi Abba bar Kahana: The Holy One, blessed be He, does not measure out a measure in a basket; rather, everything is by justice, [as it is said: "For God is the judge"] — "this one He lowers, and that one He raises" (Psalms 75:8). The Holy One, blessed be He, said to Job: Even the hair upon you — I made for it a well, and I made for it a measure, as it is said (Job 38:25): "Who has split a channel for the flood?"
It once happened with a certain priest who used to examine the plagues. His means failed him, and he sought to go abroad. He called his wife and said to her: Since people are accustomed to come to me to show me their plagues, come and I will teach you, so that you may examine the plagues. If you see that a man's hair — its well has dried up — know that he has been stricken; for every single hair the Holy One, blessed be He, created for it its own well, by itself, [from which it drinks]; once its well has dried up, the hair has dried up. His wife said to him: And if for every single hair the Holy One, blessed be He, created its own well by itself [from which it drinks] — you, who are a human being, and how many hairs are upon you, and your children are supported through you — is it not all the more certain that the Holy One, blessed be He, will provide sustenance for you? Therefore she did not allow him to go abroad.