With accent marks:
Ка́шу ма́слом не испо́ртишь.
You can't spoil the porridge with butter.
From time immemorial, porridge was loved and respected in Russia. It was cooked from wheat, buckwheat, oats, etc. To make it tastier, people added more butter.
This Russian proverb is used to say that something good can not be bad even in large quantities.
Other Russian proverbs
There are no friends for taste and color.
One head is good, but two ones are better.
Do not dig a hole for another one, you will fall into it yourself.
Put your trust in God, but don't make mistakes yourself
Better late than never.
In a quiet whirlpool, demons live.
The quieter you go, the further you'll get.
Get your sleigh ready in summer and your (horse-drawn) cart in winter.