SB 10.20.16
marga babhuvuh sandigdhas
trnais channa hy asamskrtah
nabhyasyamanah srutayo
dvijaih kalena cahatah
Translation:
During the rainy season the roads, not being cleansed, became covered with grass and debris and were thus difficult to make out. These roads were like religious scriptures that brahmanas no longer study and that thus become corrupted and covered over with the passage of time.