In this quote from Marlowe's play, Faustus has already signed his body and soul over to the devil. He is in conversation with Mephistopheles, the devil's minion. Mephistopheles tells Faustus that he knows hell is real because he has suffered its torments. However, when Faustus asks where it is, Mephistopheles is evasive, telling him it is anywhere heaven isn't and not in a particular location:
hell hath no limits, nor is circumscrib'd In one self-place
Faustus, having committed himself to hell, insists on being in denial, saying it is a "fable." He interprets Mephistopheles's words as meaning there really is no hell.
Faustus continues to elaborate on this denial in the passage quoted above. When Mephistopheles reminds him that he has signed his soul over to the devil, Faustus responds with careless disregard—"ay, and body too," meaning Lucifer will own both his body and soul. However, that matters little to Faustus at this point. Twenty-four years later, when his contract is due, seems far away, and Faustus decides that death simply means the end of pain; in other words, there is no afterlife. He says these stories of hell are "trifles": tiny details that that are unimportant, and "old wives' tales"—false stories.
Faustus's dismissal of hell is a form of dramatic irony, as the audience knows (in an uncomfortable way what he refuses to admit) that he has made a bad bargain and will have to pay the piper for all eternity. It also characterizes him as arrogant: he knows what he knows and isn't willing to listen to words that contradict what he has already decided.