Early Christian responses to suicide (source/text identification)?

I'm looking for a text I read some time ago where an Early Church writer (one of the Patristic Fathers?) responds to an argument regarding suicide put forth by some opponents. IIRC, it goes something like this: "If Christianity is true and this world is a temporary place of suffering prior to the bliss of heaven, why don't all you Christians just kill yourselves?" (Or something to that effect.) The text is the author's response--but I can't recall the text, the author, their response, or where I read it! Any help would be appreciated.