What kind of "Ish" is discussed?
Rashi: Every "Ish" in Tanach is a Gibor. He is great in the Midah of Gevurah.
What do we learn from "[Mayim Amukim Divrei Fi Ish] Nachal Nove'a Mekor Chachmah"?
Rashi: [His words are] a source of Chachmah, like a flowing river and deep water.
R. Yonah #1: A man who flows with a source of Chachmah like a river, the words of his mouth are like deep water. One cannot drink from them until he toils and draws them. So one does not understand the words of a Chacham and Navon, and does not gasp his intent, without toil to understand them. The verse warns those who hear words of a Chacham and Navon, not to think that they understood like it sounds, to grasp their intent, without considering them and putting them to his heart two or three times. Often a Chacham elaborates in his words to include a reason that will dispel any difficulty and challenge to his words; the listener will not understand until he thinks and investigates.
R. Yonah #2: This refers to verse 3. "When a Rasha comes, also disgrace comes", for he disgraces the words of the wise, and does not understand them.
Malbim: One who speaks in Divrei Chachmah, he draws deep water. Chachmah is very deep; it is hidden in the depth of the Nefesh. There is a great distance from the source to where the water comes out. Even so, the source of Chachmah is a river that flows constantly without toil. Chachmah is planted in the Nefesh, and flows and spreads from the Nefesh outside. It is the body's nature and Yetzarim of the heart that hide it. One who wants to speak and expound Divrei Chachmah must tie together ropes until he can reach the water from the depth and draw them to above.
