מדרש על במדבר 24:6

Further said R. Chama, son of R. Chanina: (Fol. 16a) "Why have Tents been placed near Streams? As is written (Num. 24. 6.) As streams are they spread forth, as gardens by the river's side, as tents which the Lord hath planted, etc. To teach you that just as streams render an impure man pure, so tents [where the Torah is studied] lift up man from the scale of guilt to the scale of merit."