Buddha's Advice to his Son -- Passage from the Majhima Nikaya

Develop a state of mind like the earth,
Rahula. For on the earth people throw
clean and unclean things, dung and urine,
spittle, pus and blood, and the earth is not
troubled or repelled or disgusted. And as
you grow like the earth no contacts with
pleasant or unpleasant will lay hold of your
mind or stick to it.

Simply you should develop a state of
mind like water, for people throw all manner
of clean and unclean things into water
and it is not troubled or repelled or disgusted.
And similarly with fire, which burns all things,
clean and unclean, and with air, which blows upon
them all, and with space,
which is nowhere established.

Develop the state of mind of friendliness,
Rahula, for, as you do so, ill-will will
grow less; and of compassion, for thus vexation
will grow less; and of joy, for thus
aversion will grow less; and of equanimity,
for thus repugnance will grow less.

- Gautama Buddha