יורה יורה ידין ידין יתיר בכורות יתיר
On דף ה עמוד א and דף ה עמוד ב [see here for the full chapter; unfortunately it doesn't mark exactly where pages 5a and 5b are], the gemara discusses how one gets to be a מומחה (expert) — someone with סמיכה (ordination), usually called here רשות ("authorization"). It also discusses what רשות actually is.
In asking the question מאי רשותא (what is 'authorization'?), the gemara tells two stories:
What is 'authorization'?
When Rabba bar (bar) Hhana went down to Babylonia, Ribbí Hhiya said to Ribbí [Yehuda Hanasi’]:
"My brother's son is going down to Babylonia."
[And Ribbí declared:]
יורה יורה, ידין ידין, יתיר בכורות יתיר
"He may instruct [in law], judge [civil cases], and release first-born animals [which are הקדש (taboo) and cannot be slaughtered unless they are blemished]."
When Rav went down to Babylonia, Ribbí Hhiya said to Ribbí [Yehuda Hanasi’]:
"My sister's son is going down to Babylonia."
[And Ribbí declared:]
יורה יורה, ידין ידין, יתיר בכורות אל יתיר
"He may instruct [in law], and judge [civil cases]; but may not release first-born animals [which are הקדש (taboo) and cannot be slaughtered unless they are blemished]."
The first two declarations, יורה יורה and ידין ידין are types of semikha that still exist today. Yoreh yoreh is given for expertise in איסור והיתר (prohibitions and permissions) — realms of Halakha such as kashrut and Shabbat. Yadin yadin is given for expertise in the civil law components of Halakha. Yatir bekhorot yatir I've never heard of in the contemporary world.
What I found particularly interesting — and very demystifying, in relation to some of my issues surrounding the rabbinate — was how before and after these two short stories about רשותא, the Talmud explains what the actual purpose of each of these authorizations was, and why one of these sages was licensed to release בכורות while the other was not.
The גמרא already explained what the point of ידין ידין authorization is — it's a legal insurance for expert judges, releasing you as the judge from personal liability in the eventuality that you make a mistaken ruling in a monetary case. Otherwise, as a layman judge, unless the litigants specifically give up their right, if you ruled that Ploni A owed Ploni B two zuzim, and then it turned out that you ruled incorrectly, you would personally be obligated to pay back Ploni A for the two zuzim they had to pay Ploni B as a result of your judgement.
In response to the difference in authorization between the two sages in the story, the גמרא explains that the reason that Rav was not authorized in יתיר בכורות יתיר wasn't because he didn't know how to evaluate biological blemishes that would release a firstborn animal from its sanctified-taboo status, but just the opposite — he was such an expert in mumin that if he were licensed to rule on such matters, people would watch him work and then go and make incorrect extrapolations based on what they thought he was doing. It's as if someone were to watch an expert driver drive stick shift, and then attempt to do so themself by wiggling the gearshift around, having missed the importance of the clutch pedal. The danger is a lack of understanding, or a miscommunication. Which brings us to the last type of רשותא...
The גמרא asks — what is the point of יורה יורה authorization? If you've learned, [and know your stuff,] why do you need to be 'authorized'?
Because of מעשה שהיה (an incident that took place; actually, a few different incidents, some of which seem to be variants on the same stories, are given here and in the parallel in the Jerusalem Talmud) where people made a mistake in practice, and justified themselves by quoting 'a student' of the sages who had passed through their town — not realizing that they had misheard or misunderstood his instructions. Because of such incidents, "that very hour they decreed that a student may not instruct unless he gets authorization from his rav." Rashi explains:
...His rav must be careful with him, so that [the student's] speech will be open, and those who listen to him will not misunderstand his words.So what's the point of יורה יורה? It doesn't point necessarily to expertise in any particular legal field, or the ability/license to analyze new situations and create legal rulings (פסק) to deal with them. יורה יורה is literally a teaching license. It's about being able to instruct the people, teach others, express Halakhic rulings in an open, understandable, approachable manner. It's about being clear in your speech (and skilled use of the blackboard?) and using formative assessment.
I'm a teacher. I get this. And it makes it a bit easier to wrap my mind around the idea of getting semikha — reshuta authorization — myself.