Exegesis:

egeneto de etc. ‘and it happened,’ cf. on 1.8 and on v. 1.

en tais hēmerais tautais ‘in those days,’ a very general indication of time without exact reference to the preceding events.

eis to oros lit. ‘into the mountain,’ to be understood in a general meaning like “into the wood”, etc., and best rendered as “into the hills” (Revised Standard Version).

proseuxasthai ‘to pray,’ final infinitive dependent upon exelthein.

kai ēn dianuktereuōn en tē proseuchē tou theou ‘and he spent the night in prayer to God.’ The genitive tou theou is objective and indicates to whom the prayer was directed.

dianuktereuō ‘to spend the whole night,’ i.e. in doing something.

Translation:

Went out, or, ‘went up,’ because of what follows (e.g. in Marathi, Batak Toba).

To pray, see references on 1.10.

All night he continued in prayer to God, or, “(he) spent the night in prayer to God” (New English Bible), ‘all-night-long he prayed to God’; the latter rendering may require a durative form, but in several languages this aspect is already sufficiently indicated by the temporal qualification. If the term for ‘to pray’ includes a reference to God, the rendering of this verse will have to be adjusted, cf. e.g. ‘he went out/up … to speak to God; the whole night he spoke (or, he spoke to him, or, he did so).’

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.