Write Injuries in Dust, Benefits in Marble.

Benjamin Franklin (1706-1790) American statesman, scientist, philosopher, aphorist

Poor Richard’s Almanack, “August” (1747)
    (Source)

As with so much else of Franklin's, this phrase is not without earlier forms, e.g.: Thomas More, History of King Richard III (1513):

For men use, if they have an evil turn, to write it in marble; and whosoever does us a good turn, we write it in dust.

Or see Shakespeare, Henry VIII 4.2.45-46 (1613):

Men's evil manners live in brass, their virtues
We write in water.

Variants include "but kindnesses in marble" or "but kindness in marble."

This also shows up as a French saying in various forms:

• "Ecrivez les injures sur le sable, mais les bienfaits sur le marbre."
• "Écrivez les injures sur le sable, gravez les bienfaits sur le marbre."