How did wine of Prugaisa and [bathing in] water of the Deyumeses sever the 10 Shevatim from Yisrael?

Rashi: They pursued these pleasures, neglected learning and sinned.

Maharal: Physicality opposes the spiritual. One who pursues physical desire, he distances from the level of what is separated. Water is indulgence of the body, and "Yayin Yesamach Levav Enosh." The 10 tribes veered from the level of Yisrael - straightness.

Maharsha: "Ha'Shosim b'Mizrekei Yayin... Yiglu b'Rosh Golim" (62b) - they drank in a pleasurable way.

What is the significance of 'ha'Cheres Hayah Libam'?

Maharal: He did not forget [even the forms of the letters] to the point that he erred to read so. Rather, Hash-m caused him to read so, to arouse him that he forgot his learning.

Maharsha: "Ha'Chodesh ha'Zeh Lachem" was the first Mitzvah given to Yisrael. R. Yitzchak asked, the Torah should have begun with this! He erred, for Dalet resembles Reish, and Chaf resembles Beis (103a); also Yud resembles Zayin a little. The mistake hinted that when he was connected to Chachamim, his heart was a 'gushing spring' (he outweighed all other Chachamim - Avos 2:8), and now it became hard like earthenware.

Iyun Yakov: The change added 181 to the Gematriya, i.e. Kafa, like "Kaf'u Sehomos" - they became hard like a rock (Rashi), So became his heart, to the point that he did not know what he says! The other way, the letters spell Afak - he took out of his heart springs of Chochmah.

Ya'avetz: This hinted to him that these pleasures made the 10 Shevatim lose Yir'as Shamayim, and their hearts became hard like earthenware.

Why did he say 'exile yourself to a place of Torah'?

Rashi: If you are a Chacham, go to where other Chachamim are. Do not say 'they are Talmidim - they should come to me! Why should I exile myself?'

Why did he say 'do not say that Torah will follow you, for your colleagues will cause you to retain it'?

Rashi: Rather, go to your colleagues. When you learn one tractate, they learn others, and you hear it. This helps you to remember them.

Bartenura (Avos 4:14) #1: Do not say that Torah will follow you, that your colleagues will cause you to retain it. i.e. they will go to learn from a Rav, and you will learn from them. It is better that you learn directly from a Rav!

Bartenura (Avos 4:14) #2: Even if you are very sharp, your Torah will endure only if you debate with your colleagues.

Maharal: Do not say, 'I need not exile myself - Torah will come to me.' When you go to a place of Torah, your colleagues will cause you to retain it - you can ask! He said so, for he went to a place without Torah, and forgot his Torah.

Why did he say 'do not rely on your understanding'?

Rashi: Do not say, I am a great Chacham, and I remember well. When I learn this Perek or tractate, I will not forget the other.

Maharal: Do not say, I need not ask.