When you teach your son, you teach your son's son.
The Talmud in Wikipedia
Chop your own wood, and it will warm you twice.
(July 30, 1863 - April 07, 1947)
We know it is out there, we see it in our syringe exchange clients and elsewhere. And it's in other communities as well.
If a man smiles all the time, he's probably selling something that doesn't work