The Master said, At fifteen I sat my heart on learning. At thirty, I had planted my feet firm upon the ground. At forty, I no longer suffered from...

The Master said, At fifteen I sat my heart on learning. At thirty, I had planted my feet firm upon the ground. At forty, I no longer suffered from perplexities. At fifty, I knew what were the hidings of Heaven. At sixty, I heard them with a docile ear. At seventy, I could follow the dictates of my own heart; for what I desired no longer overstepped the boundaries of right."

What tradition could this derive from? Who said it? What are its implications in the context of the tradition?