Why does it say "li'Schok"?
Ibn Ezra: It is one who leans to laughter.
Rashbam: I said about Sechok. Refer to 2:2:4:1.
Metzudas Tziyon: This is laughter that comes from Simchah.
What is "Mehulal"?
Shabbos 30b, Rashi there: It is praiseworthy
Rav Sadya Gaon: It is lowliness and a bad Midah.
Rashi: It is mixed with crying and sorrow. R. Avigdor (from Koheles Rabah 2:2 and Zevachim 102a) -Elisheva bas Aminadav had five special causes for joy on the day the Mishkan was inaugurated. Her Yavam (brother-in-law, i.e. Moshe) was king. Her husband Aharon was Kohen Gadol. Her brother (Nachshon) was the Nasi [of Shevet Yehudah]. Her son (Elazar) was the Segan (next in line to be Kohen Gadol). Her grandson (Pinchas) was Mashu'ach Milchamah. In the end, she saw [two of] her sons (Nadav and Avihu) burned, and her Simchah turned to mourning.
Rashbam, Metzudas David: It is lunacy. Ri Kara - it is like "va'Yis'holel b'Yadam" (Shmuel I, 21:14).
Rid: It is lunacy and Hevel. Sometimes one rejoices, and it is proper to cry, for he does not know what will come from the laughter!
R. Avigdor (from Koheles Rabah 2:3): This is disorder and laughter that Nochrim do in their theaters and circuses.
Seforno: It is not directed towards good purposes.
The Gemara (Shabbos 30b) explains that Sechok is Mehulal (praiseworthy). It says below "Tov Ka'as mi'Sechok" (7:3; even anger is better than laughter)!
Shabbos 30b: The anger that Hashem has against Tzadikim [to punish them] in this world is better than His laughter with the Resha'im in this world 1 . The Sechok that Hashem will have with Tzadikim in the world to come is praiseworthy.
R. Avigdor (7:3): Anger against Tzadikim causes them to merit the world to come. For Resha'im, "u'Meshalem l'Son'av El Panav Leha'avido" (Devarim 7:10; they are rewarded for their Mitzvos here, and get no share in the world to come).
Why does it say "ul'Simchah"?
Rashbam, Ibn Ezra: I said about Simchah. The prefix Lamed is like in "Imri Li Achi Hu" (Bereishis 20:13), "va'Amar Pharaoh li'Vnei Yisrael" (Shemos 14:3), "Ka'asher Diber Lach" (Devarim 26:18).
What is the meaning of "Mah Zo Osah"?
Rav Sadya Gaon: There is no benefit and advantage from it.
Rashi: What good does it do? [Ri Kara - Simchah of Mishteh,] its end is sadness!
R. Avigdor: Why should a Chacham enter [theaters and circuses of Nochrim]?! From here, they ruled that a Talmid Chacham may not go to see Simchah of Goyim.
Here it says that that Simchah is worthless. Below, it says "v'Shibachti Ani Es ha'Simchah" (8:15)!
Shabbos 30b Shlomo lauds the Simchah one has in a Mitzvah 1 (Rashi - Simchah that is itself a Mitzvah, e.g. to gladden a Chasan and Kalah), but sees no value in other Simchah.
Ibn Ezra (7:3): Those who toil in this world and do seek Chachmah, and they are happy, they are better than those who worry about Hevel.
Below (9:11), Ibn Ezra says that Shlomo retracted from praising Simchah. Perhaps this verse was after his retraction. (PF)
30b: We learn from this that the Shechinah does not rest [on a person] amidst sadness, laziness, Sechok, lightheadedness, conversation or idle words, only amidst Simchah of a Mitzvah - "v'Hayah k'Nagen ha'Menagen va'Tehi Alav Ru'ach Hashem." Similarly, one must learn Halachah amidst Simchah. Going to sleep amidst Simchah will cause good dreams.
