todays daf insights(daf6)from Kollel Iyun Hadaf

when there a leap year we have an Adar rishon Poskim
1. Shulchan Aruch (OC 697:1): On the 14th and 15th of
Adar Rishon we do not say Tachanun or "Ya'ancha
Hashem b'Yom Tzarah". Eulogies and fasting are
forbidden, but other laws of Purim do not apply.
Some permit even eulogies and fasting.
i. Gra (DH v'Yesh Omrim): From the Seifa (the only
difference between Adar Rishon....) we inferred
that Simchah and Mishteh are the same in both.
The lenient opinion holds that the Seifa must
refer to the Reisha, when the year was made
Me'uberes after they read the Megilah. It
cannot discuss when we knew in advance that the
year will be Me'uberes, for we would never
think that one must read the four Parashiyos in
both months. The Ran rejects this; the Mishnah
means, even in such a case R. Shimon ben
Gamliel requires repeating the Parashiyos in
Adar Sheni.
2. Rema: The custom is like the first opinion. Some
obligate extra Simchah and Mishteh on the 14th of
Adar Rishon; this is not our custom. In any case it
is good to increase a bit to fulfill this opinion.
"V'Tov Lev Mishteh Samid".
i. Beis Yosef (DH u'Pashut): Some infer that the
only difference between Adar Rishon and Sheni
are Kri'as ha'Megilah and Matanos la'Evyonim,
but Simchah and Mishteh are the same in both.
Tosfos (6b DH v'R. Eliezer) rejects this,
because the Gemara infers that they are the
same regarding eulogies and fasting, but not
regarding Simchah and Mishteh. SMaK says that
even though we increase Simchah and Mishteh on
the 14th and 15th of Adar Sheni, in Adar Rishon
we do so only on the 14th. This is because the
Gemara says that the only difference between
the *14th* of Adar Rishon... It does not
mention the 15th. However, perhaps it only
mentions the primary day. There is no Isur
Melachah in Adar Rishon. Even in Adar Sheni the
Isur depends on custom. Nowadays the custom is
not to increase Simchah and Mishteh in Adar
Rishon. Nevertheless, we do not say Tachanun or
"Ya'ancha Hashem b'Yom Tzarah" because they are
days of a miracle and salvation.
ii. Mishbetzos Zahav (1): If someone vowed to fast
on Purim Katan it takes effect, for it is a
mere custom not to fast. However, if he vowed
to fast on Mondays and Thursdays, presumably he
did not intend to forbid Purim Katan.
iii. Eshel Avraham (2): The Rema brings "V'Tov Lev
Mishteh Samid" to suggest increasing Simchah
also on the 14th of Adar Rishon. The Magen
Avraham (2) explains that this refers to
Simchah in Avodas Hashem.