Rashi ¹ : It is David. Radak, citing Chazal and Targum Yonasan: The verse hints to the Gevuros (strengths) of David.

Radak #1 (based on Yalkut Shimoni 145): Some say that the verse hints to Yo'av. He was a great Chacham and Rosh Sanhedrin - "the third head makes me wise."

Radak #2: The simple meaning is, he was one of David's Giborim, and the head of them.

Rashi: I sit on the Sanhedrin, and this makes me wise.

Radak #1: He used to sit in the Yeshivah of Torah.

Radak #2: [Yo'av] was a great Chacham and Rosh Sanhedrin - "the third head makes me wise ¹ ."

Radak #3: He sat among the Sanhedrin and Chachamim.

Rashi: This (sitting on the Sanhedrin) makes me wise.

Radak: It is an adjective; it describes his Chachmah.

Radak #1: There, "Ben" is like 'Ish', like 'Ben Chayil.' I.e. he was a man of Chachmah.

Radak #2: His father was Tachkemoni or Chachmoni; these are the same. Adino was his son.

Malbim citing Mahari: His real name was Adino ha'Atzni. He is called Yashav'am Ben Chachmoni, for he sat among Chachamim at the head of the nation, and he was a Ben Chacham.

Rashi: He is a father (head) in beauty, Chachmah and Gevurah, like it says "Nevon Davar v'Ish To'ar" and "Gibor Chayil" (Shmuel I, 16:18).

Radak: He was the head of three Avos.

Radak #3: He [sat among the Sanhedrin and Chachamim, and] was the head of them. It is as if it says Rosh ha'Shelishim ¹ . Similarly, "la'Kari vela'Ratzim" (Melachim II, 11:4) it is as if it says la'Karim. Shelishim is an expression of grandeur and honor, like "ha'Shelish Asher la'Melech" (Melachim II, 7:2) and "u'Mivchar Shalishav" (Shemos 15:4).

Malbim: He was not head of the three Giborim, for Avishai did like him, and it says that Avishai did not come among the three (verse 19)! Rather, he was head of 30 Giborim (like it says in Divrei ha'Yamim I, 11:11). Rather, he was the biggest Chacham of the three [listed after this].

Rashi: When he engages in Torah, he wraps and ties (Radak - indulges) himself like a worm. [Adino] is like "Ma'adanos Kimah" (Iyov 38:31). [Ha'Atzni hints that] when he went out to war, he is hard like a tree, and kills 800 people in one war.

Radak: There were two wars. In one he killed 800, and in the other, 300.

Malbim: There it teaches that after killing 300, he would wave his spear easily to and fro. Here it teaches that after killing 800, he investigated deeply in Torah.

Malbim citing Mahari: Here it lists only those who were with David in all his wars. There it lists also those who [only] helped solidify his kingship.