With accent marks:
В чужо́й монасты́рь со свои́м уста́вом не хо́дят.
Don't bring your set of rules in a foreign monastery
This Russian proverb condemns and makes fun of those who are trying to live and act in a foreign community according to their own rules. When we are not at home (or not in our own country), we should follow the rules, orders and customs established there.
The closest English equivalent is: when in Rome, do as the Romans do.
The orogins of the proverb:
Before the revolution, there were many monasteries in Russia, and each of them had its own set of rules which all members of the monastery followed. The same rules applied to new arrivals.
The monks only followed their own set of rules. If they were transferred to another monastery, then they had to follow their (new) rules. All attempts by an outsider to amend those rules were not welcome.
Other Russian proverbs
The best is the enemy of the good.
There are no friends for taste and color.
Fear has big eyes.
An old friend is better than two new ones.
Bitter truth is better than sweet lies.
You see your friends in the times of trouble.
Beast runs towards the hunter.
Do not chop the branch you sit on