Exegesis:

ti katheudete ‘why are you sleeping?,’ expressing astonishment rather than inquiring after a reason. katheudō, cf. on 8.52.

anastantes proseuchesthe ‘rise and pray,’ i.e. rise from your lying position and stand on your feet, cf. on v. 41.

Translation:

Why do you sleep?, or, ‘how is it possible that you are asleep?,’ ‘do you really sleep now?.’

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.