Bablyonian Talmud, Book 5: Tracts Aboth, Derech Eretz-Rabba, Eretz-Zuta, and Baba Kama (First Gate), tr. by Michael L. Rodkinson, , at sacred-texts.com
A SCHOLAR must not eat standingly, nor lick his fingers, nor yawn in presence of others. Talk little, laugh little, sleep little, indulge little in pleasure, say little "yea" and little "nay." One has always to know with whom he is sitting, near whom he is standing, with whom he is eating, with whom he is conversing, for whom he signs contracts and notes of debt. By four things the scholar is recognized: his pocket, his goblet, his anger, and his dress; and, some say, even his talk. The beauty of the Law is wisdom; the beauty of wisdom is modesty; the beauty of modesty is the fear of Heaven; the beauty of the fear of Heaven is noble performance; the beauty
of noble performance is secrecy (i.e., not publicly, for the purpose of being praised). One shall not be awake, etc. (see above).