"ὁ πιστεύσας καὶ βαπτισθεὶς σωθήσεται, ὁ δὲ ἀπιστήσας κατακριθήσεται."

That's the closest we can get, although Jesus would have assumedly spoken these words in Aramaic, not Greek.

Source: http://bibletranslation.ws/trans/markwgrk.pdf