With accent marks:
Долг платежо́м кра́сен.
The beauty of a debt is its payment
This proverb reminds us that we should always pay our debts back.
The word красен here comes from красный (red). In the old times, красный meant красивый.
The closest English equivalent is "One good turn deserves another".
Other Russian proverbs
A well-fed man does not understand a starving one.
Measure seven times, cut one.
What you will sow, that you will reap.
They do not seek good from good.
Without labor, you can not even catch a fish in the pond.
Start taking care of the dress while it's new, and of your honor while you are young.
(lit.) Whoever gets up early, God gives him
Appetite comes with eating.