Will someone please explain all the details of the usage of the phrase 'it's high time we leave' or 'left' with references from the masters of english language. I will be thankful.

I don't know the origins, but it means that the time has passed, and it's after the time to leave. Saying "it's high time we leave" means that the person has to leave, and that they probably should already have left.

I just want references from the masters of english language using this sentence in any of their books. I will be thankful to any person helping me in this ordeal.

Thanks/.

High time (http://www.phrases.org.uk/meanings/177000.html)