Why does it say "Yafutzu Mainosecha Chutzah"?
Rashi: In the end you will acquire Talmidim and teach rulings to the Rabim, and acquire a reputation.
Malbim: His teachings will spread to his sons and Talmidim.
What is the meaning of "ba'Rchovos Palgei Mayim [Chayim]"?
Rashi: Your water (teachings) will spread in streets of the city.
Malbim: Chutz is in back of the houses. Only the household is found there. Rechov is the wide place in front of the houses - there is Reshus ha'Rabim. Afterwards, all of Yisrael will draw and drink the water of his Chachmah. This is Palgei Mayim, which spread past their banks - 'like an overpowering spring and a river that does not cease' (Avos 6:1).
Ma'alos ha'Torah (DH Yafutzu): Divrei Torah are compared to Mayim Chayim. Just like Mayim Chayim is (flows) forever, so Divrei Torah are Chai forever - "Chayim Hem l'Motze'eihem" (4:22).
