Origin
The proverb has been traced back to Geoffrey Chaucer’s ‘Troilus and Criseyde’. George Herbert wrote in 1651. This saying is first cited in the United States in ‘William & Mary College Quarterly.
Explanation
Do not criticize others if you have similar weaknesses yourself. It means those who are vulnerable should not attack others. It can also mean that it is strategically weak. By calling another out, people will see their insecurities. A person should not criticize others for having the same faults. We shouldn’t complain about others if we are as bad as they are. ‘To live in a glass house’ is used as a figure of speech referring to vulnerability.It means that when you have done something yourself, you shouldn’t criticise other people for doing the same-with the implication they can then criticse you.If you throw a stone in a house made of glass, what happens? It will break the glass. This is the metaphor behind this expression.
Examples
Jill : Richard was drinking a lot at the office party. Jane: I noticed you had quite a few cocktails yourself. People who live in glass houses shouldn’t throw stones.
People who live in glass houses shouldn’t throw stones, so if you failed your exam you shouldn’t laugh at Pauline for her bad marks.