With accent marks:
От добра́ добра́ не и́щут.
They do not seek good from good.
Few people know that this is only part of the proverb. Its full version sounds like this: "От овса кони не рыщут, а от добра добра не ищут" (Horses do not roam from oats, but they do not seek good from good). It means that if the horses are fed, they will not run away. If a person is doing well at home, he will not leave the family.
In its shorter version the proverb acquired a second meaning: when doing good to people, one should not expect the same from them. You need to do good selflessly.
Other Russian proverbs
Do not look at a given horse's teeth.
The forbidden fruit is sweet.
The apple never falls far from the tree.
What you will sow, that you will reap.
A bird is visible by its flight.
Some to the forest, some for firewood.
Repetition is the mother of learning.
Man does not live thanks to bread alone.