Where did Christ tell us to shut ourselves away in monasteries or convents?

Nowhere. But He invited some people to renounce all things and to follow Him by close imitation. “If you wish to be really perfect, sell all you have, give to the poor, and come, follow Me.” If a man marries he cannot do that. He has a duty to his wife and children, and cannot sell the house and furniture over their heads, leaving them stranded. From the very beginning many Christian young men and women renounced the prospects of marriage and property for the love of Christ. The Church arranged community houses wherein the members were to own nothing, merely receiving shelter from the weather and necessary food and clothing. For the rest they were to give themselves to prayer and to works of piety and charity, instructing children, preaching the Gospel, nursing the sick, or feeding the hungry and destitute. Later these houses were called monasteries, after the Greek word Monos, meaning alone or single. The fact that those who have renounced all in accordance with the invitation of Christ live in monasteries or convents makes no more difference than if they lived in tents.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty