Exegesis:

elegen de parabolēn autois ‘then he told them a parable.’ autois refers to the disciples to whom 17.22-37 was addressed. de marks continuation.

pros to dein pantote proseuchesthai autous kai mē egkakein ‘to show that they must always pray and not give up.’ The clause is best understood as going with elegen and indicating Jesus’ intention in telling the parable. The impersonal dei marks necessity.

egkakeō ‘to become tired,’ here either in an absolute sense, ‘to lose heart,’ ‘to become discouraged,’ or, with the participle proseuchomenous understood (cf. 2 Thess. 3.13), ‘to give up,’ scil. praying. The latter is preferable.

Translation:

Parable, see on 8.4.

To the effect, or, “to make it clear” (The Four Gospels – a New Translation), “to teach them” (Good News Translation); or, ‘its-content, or, its-gist (being)’ (Balinese, Javanese). The following clause may better be shifted to direct discourse, “You should always pray and never lose heart, or, give up”.

Always, or, ‘again and again.’

To lose heart, or ‘(to become) desperate (lit. hope being-broken-off)’ (Bahasa Indonesia); cf. also Mark 6:50 on the opposite expression “to take heart”. Following the interpretation preferred in Exegesis one may say, “to slacken” (The Four Gospels – a New Translation), ‘to weary’ (Sranan Tongo, similarly Bible de Jérusalem).

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.