Have you had a kindness shown?
Pass it on;
‘Twas not given for thee alone,
Pass it on;
Let it travel down the years,
Let it wipe another’s tears,
‘Til in Heaven the deed appears –
Pass it on.

~ Henry Burton 

Greed’s worst point is its ingratitude.

~ Seneca

Ingratitude is a nail which, driven into the tree of courtesy, causes it to wither; it is a broken channel, by which the foundations of the affections are undermined; and a lump of soot, which, failing into the dish of friendship, destroys its scent and flavor.

~ Giambattitsta Basile