Why does it say "va'Ydaber"?
Malbim: In addition to the Chachmah in his heart, he spoke with Ru'ach ha'Kodesh and composed Seforim.
What are "Sheloshes Alafim Mashal"?
Rashi: They are three collections of teachings 1 via parables. It says "Mishlei Shlomo" three times in Sefer Mishlei (1:1, 10:1, 25:1). Alshich (Mishlei 1:1) - he composed them at three times - when he was only Ben David (but not yet king), when he was king only over Yisrael, and when he was king over all Nochri kings.
Rashi citing Rabanan in Bamidbar Rabah 19:3: On every verse he gave 3,000 parables; for each parable, he had 1,005 reasons.
Radak: They were lost to us; many Seforim were lost due to exile.
Radak citing R. Shmuel bar Nachmani in Bamidbar Rabah 19:3: He said only about 800 verses (in all, in Mishlei, Shir ha'Shirim and Koheles)! Rather, for every verse he said, there are two or three reasons 2 , e.g. "Nezem Zahav va'Chali Chesem Mochi'ach Chacham Al Ozen Shoma'as" (Mishlei 25:12).
Malbim: This is like "va'A'alefcha Chachmah" (Iyov 33:33).
Imrei Yosher (on the Midrash, 19:3): There is Nigleh and Nistar (revealed and hidden); the Torah has clothing, body and Neshamah, like the Zohar says. To reach 3,000, the average verse would have to have about four reasons! Likutim (on 19:3) - this is why Rabanan explained differently (refer to 5:12:2:2)! Maharzu (on 19:3) - Alafim is like teachings (each verse teaches three matters).
What are "Shiro Chamishah va'Alef"?
Rashi: The five are these three [collections of parables], Shir ha'Shirim and Koheles. "Va'Alef" means that each was worthy to learn.
Rashi citing Bamidbar Rabah 19:3: Refer to 5:12:2:2.
'Rashi' (Divrei ha'Yamim II, 9:10, citing Eliezer Sharim): They are Chulin songs that he composed for people to sing in front of him for his pleasure.
Malbim: This refers to Shir ha'Shirim, which is composed of five songs; the last begins "Achos Lanu Katanah; "Ish Yavi b'Firyo Elef Kasef; ha'Elef Lecha Shlomo" (8:8, 11-12) - the Shir is called Elef.
