FAUSTUS: What doctrine call you this, Che sera, sera:
What will be, shall be? Divinity, adieu!

Christopher "Kit" Marlowe (1564-1593) English dramatist and poet

The Tragicall History of the Life and Death of Doctor Faustus, Act 1, sc. 1 (sc. 1), l. 76ff (1594; 1604 “A” text)
    (Source)

Giving up on Christian doctrine, since it teaches that all are sinful, and that sinfulness condemns one to death and damnation. (Faustus ignores the ideas of repentance and salvation.)

These lines show up as well in the 1616 "B" text (ll. 75-76).

This is one of the earliest mentions of the phrase che sarà sarà, which shows up first as a 16th Century English heraldic motto.