This quote has been attributed to many different artists, from Igor Stravinsky to Pablo Picasso and who knows, Yogi Berra probably even said something like it once, in regard to base stealing. But T.S. Elliot was among the first to deliver more than a one-line quote. What does it mean, to steal? Here's how T.S. Elliot defines it: One of the surest tests [of the superiority or inferiority of a poet] is the way in which a poet borrows. Immature poets imitate; mature poets steal; bad poets deface what they take, and good poets make it into something better, or at least something different. The good poet welds his theft into a whole of feeling which is unique, utterly different than that from which it is torn; the bad poet throws it into something which has no cohesion.
The idea, then, is to transform the literary ideas you take from others into something completely new.