Beard Hairs
Question
Why Do Some People Put Their Beard Hairs in Sefarim (Books)?
Answer
Yes. It’s true. Some people have the practice to place picked or fallen beard hairs into a sefer. Some only do so if the beard hair comes out while learning. It is not completely clear how this practice, likely with kabbalistic influence, began.
It is noted that Rabbeinu Tam once sent a letter to someone and in the envelope he included some of his beard hairs. There is reason to believe, however, that the reason he placed his beard hairs in the letter was in order to convey his strong feelings about the topic he was writing about and not in compliance with any custom or act of piety. (1)
Nevertheless, a number of authorities explicitly rule against placing beard hairs in a sefer, as it is forbidden to place almost anything in a sefer! (2) Furthermore, those who open a sefer only to find it full of someone else’s hairs will be disgusted, and it is forbidden to do something that others find disgusting. (3)
Bottom line, is that this should not be done.
Source
1. See Shitta Mekubetzet, Zevachim 18b.
2. Torah Lishma 306; Yalkut Yosef, Kitzur Shulchan Aruch 153:17.
3. Chagiga 5a.
4. Binyan Shalom 6:137.
5. Likutei Maharich Vol. 1 p. 106.
6. Igra D’pirka 337. See also Otzar Teshuva 1:98 for more on the practice.