- ketav (writing),
- shehitah (kosher slaughter) and
- milah (circumcision).
Rav Hananiah bar Shelemia quotes Rav as teaching three additional things:
- kesher shel tefillin (phylactery knots)
- birkat hatanim (blessings made at weddings)
- tzitzit (ritual fringes).
The Me’iri explains that although we expect that a Torah scholar would devote his energies to learning theory, still there are certain practical things that he must learn to do. These are things about which people run to ask the scholar questions, and if he is unable to respond, his reputation will be tarnished. Others suggest that a scholar must take an interest in community affairs and these are basic issues that he must deal with.
Rashi explains that the requirement to know ketav – writing – refers to signing his name, since he will have to sign documents as a witness or when making a ruling; Rashi appears to assume that although every Jewish child was taught to read, not all learned how to write. The Yam Shel Shlomo suggests that this means that he must learn to express ideas clearly in writing so that he can pen letters and author rulings and responsa. According to the Maharsha, the requirement is to learn to be a scribe so that he can write tefillin and mezuzot for himself and for others.
The Gemara explains that Rav Yehudah did not include the second three things “because they are common.” Rashi explains this to mean that since they are common, everyone knows how to do them and there is no need to make it a special requirement for scholars. The first three, however, are performed by specially trained individuals. Rabbenu Gershom takes a different approach, arguing that it is the first three that are common, which is why the scholar must make sure to learn them, as opposed to the latter three that are only needed on occasion.