Exegesis:

V. 25 begins with a subordinate temporal clause. The main clause is either kai apokritheis erei humin ‘he will answer and say to you,’ or does not begin till v. 26, tote arxesthe legein ‘then you will begin to say.’ The former interpretation is more probable.

aph’ hou an ‘when once,’ modifies three verbs, i.e. egerthē, apokleisē and arxēsthe.

egerthē ho oikodespotēs ‘(when once) the master of the house has got up.’ egerthē refers here to getting up after sitting down at table.

kai apokleisē tēn thuran ‘and has locked the door.’

apokleiō ‘to lock,’ synonymous with kleiō (11.7).

kai arxēsthe exō hestanai ‘and you begin to stand outside.’ Strictly speaking they were outside all the time, and arxēsthe indicates a new situation, i.e. that of their being locked out.

kai krouein tēn thuran legontes ‘and to knock at the door, saying.’

kurie, anoixon hēmin ‘sir, open (the door) for us.’

kai apokritheis erei humin ‘he will answer and say to you.’ kai at the beginning of the apodosis is a Hebraism.

ouk oida humas pothen este ‘I do not know where you come from,’ i.e. ‘I do not know of any relationship with you.’

Translation:

The sentence when once…, ‘Lord, open to us’ (rendering a Greek subordinate clause) may better be rendered as two co-ordinate sentences, e.g. ‘the moment/time will come that the householder … shuts the door; then you will begin…, saying, “Lord, open to us” .’

The householder, i.e. the one who has authority in the place referred to in v. 24; hence ‘the one who rules there, or, owns that place,’ may help to bring out the connexion with what precedes.

Shut the door, cf. 11.7.

You will begin to stand outside and to knock …, or, to bring out the new situation, “you may find yourselves standing outside and knocking…” (Phillips). Outside, or ‘at-the-other-side,’ i.e. than the householder who is inside (Tae’).

For knock at the door and open to us, or, “let us in” (New English Bible), cf. 11.9.

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.