Rif

Practical Focus

The Rif generally quotes only relevant passages of the Gemara and leaves out points that aren't accepted at the end of the sugya. That said, there are some exceptions to be aware of.

1. Even though the Rif generally only records Halachot that are relevant nowadays, for example, to the exclusion of Kodashim, if a Halacha that is generally relevant has a detail that is not, he will write the entire Halacha including the detail. Moreover, if there is some relevant Halacha or Chiddush to derive from the irrelevant Halacha, then that Halacha will be included, as well, but practical but uncommon Halachot will not be recorded.
2. If a din that does not appear to be subject of debate in the Gemara is only recorded partially in the Rif, it's an indication that the Rif holds the omitted segments are not accepted in practice.
3. Periodically, the Rif will quote a Tosefta by opening with Tanu Rabbanan, because the end of that Tosefta is quoted in the Gemara.
4. When the Gemara presents two Baraitot that each derive the same Halacha but from different sources (Tanya and Tanya Idach), the Rif will quote both.
5. However, some say he will not quote a Baraita that is not in line with the accepted Halacha.
6. When the Gemara questions an assertion based on the words of an Amora, it's an indication that his view was accepted.
7. If the Gemara presents an answer that unanimously resolves a difficulty in the Mishna but then continues to present additional resolutions from other Amoraim, which we would assume like in practice, the Rif will still quote the unanimously agreeable upon answer, even if it's not LeHalacha.
8. The Be'er Sheva advises one to not be surprised if the Rif omits the okimta of the Gemara in favor of his own original understanding, as he rathers to minimize Machaloket than quote the Gemara. The Yad Malachi argues lengthily against this approach and posits that the Rif merely omits Gemaras he feels to not be Aliba deHilcheta. The Rif and Rambam aren't Amoraim who have the ability to decide unresolved issues in the Gemara!
9. Similar to the rule of Stam vaYesh in reading Shulchan Aruch, when the Rif states that the Halacha follows a certain ruling but there are those who disagree, he intends to rule like the former and is only sharing the latter to transmit the rulings of earlier generations.
10. When the Rif writes two reasonings, his intention is to rule like the second.
11. If the Gemara presents an alternative answer (איכא דאמרי), the Rif will pasken like it instead of the first answer, even if the second answer is more stringent and the case is only of DeRabbanan nature.
12. Unless explicitly stated by the Rif that one should be stringent, the assumption is that a lenient approach is taken with unresolved inquiries of the Gemara (Tiku)
13. Similar to Rashi, the Rif will only explain a Halacha with the words כלומר or פירוש to offer specifically this interpreation over a possible alternative one that would be subject to some question.

Rav Hai Gaon

1. "The Gaon" in the Rif's jargon most probably refers to Rav Hai Gaon.
2. When the Rif cites a ruling of Rav Hai Gaon without explicitly agreeing with it, the Raavad and Rosh believe that he is disagreeing, while the Ramban and Rashba argue he is agreeing since he didn't state otherwise. The Yad Malachi finds that the Rashba is more logical, a great number of Rishonim side with him on this matter, and the former opinion isn't so clear in the first place.
3. After presenting a Machaloket, if the Rif concludes with citing Rav Hai Gaon as taking a certain side, that would indicates he agrees with that side, as well.

Misc.

1. The Rif's teachers were Rav Nissim Gaon and Rabbeinu Chananel.
2. There is controversy regarding the reliability and authorship of the Rif's responsa.
3. Rabbeinu Yitzchak ben Yaakov Alfasi, the Rif, had a grandson, Rav Yitzchak ben Reuven, who is known as the Baal HaShe'arim. Some Poskim weren't aware of this and mistakenly posed contradictions between the writings of the two.