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
Оne sees the mote in another's eye and ignores the log in his own.
Water wears away a stone.
Fear has big eyes.
The apple never falls far from the tree.
Make a fool pray to God - he will break his forehead.
Strike the iron while it's hot.
Do not look at a given horse's teeth.
The demon is not as scary as he is depicted.