explain the meaning of the quotation by Emerson that say there is a time in every man's education when he arrives at the conviction that envy is ingnorance; that imitation is suicide; select a supporting quotation

This quotation comes from the early part of Emerson's "Self Reliance," which focuses on the importance of individualism and the self. What Emerson is saying is that for every person, eventually there will come a moment when one realizes that relying on other people's ideas, wanting what other people want, or striving to be anything other than the way one was born is to do oneself a disservice. After the fragment you have quoted, Emerson goes on to say:

The power which resides in him is new in nature, and none but he knows what that is which he can do, nor does he know until he has tried.

This secondary quotation serves to illuminate Emerson's point, in which he enumerates the various ways in which a man who has not yet come to understand the importance of self-reliance may be damaging himself emotionally. Envy, Emerson is saying, comes from a place of ignorance: only a man who does not realize that he has a special and particular power in himself would envy what others have or can do. Likewise, to imitate someone else and seek to copy them is "suicide" in that this is the equivalent of murdering one's own individualism: in imitating someone else, we are preventing our own special power, given to us by nature, from expressing itself. Education, Emerson says, is the means by which men come to this understanding, and, having reached it, they can never return to ignorance.