Exegesis:
The verse is a nominal clause consisting of three phrases: (a) to eleos autou ‘his mercy,’ subject of the clause, (b) eis geneas kai geneas ‘for generations and generations,’ and (c) tois phoboumenois auton ‘for those who fear him.’ Either (b) or (c) may be interpreted as predicate of the clause, preferably the former, since the word order of the verse suggests a closer relationship between (b) and (a) than between (c) and (a).
kai to eleos autou ‘and his mercy.’ The verse is a free quotation of the Septuagint translation of Ps. 103.17.
eleos ‘compassion,’ ‘pity,’ in ch. 1 always of God towards man; the Hebrew word used in Ps. 103.17, which colours the meaning of eleos here, is usually understood as ‘solidarity,’ cf. “steadfast love” (Revised Standard Version).
eis geneas kai geneas ‘for generations and generations’ or ‘for ages and ages,’ a well known time-phrase in the Septuagint, cf. e.g. Ps. 32 (in Hebrew 33).11. The phrase indicates continuation in successive generations or ages; cf. ‘all generation,’ i.e. people in age after age, in v. 48.
tois phoboumenois auton ‘for those who fear Him.’
phobeomai ‘to fear’ is sometimes (18.2, 4; 23.40) used with theos as its object as a translation of the well known ‘fear of the Lord’ in the Old Testament, a comprehensive expression of the relationship of man with God, with the emphasis on the reverence towards God on the side of man.
Translation:
If phrase (b) is taken as the predicate (see Exegesis), the first line of this verse becomes, ‘his mercy is from generation to generation,’ and expresses that God’s mercy is everlasting; the second line, i.e. phrase (c), then serves to qualify that mercy by mentioning its recipients, e.g. ‘(that is,) to those who fear him.’ If one has to shift to a verbal construction, e.g. ‘he shows mercy to (or, mercy-es, i.e. has mercy on),’ and the verb requires an object, one may add ‘people,’ ‘his people,’ ‘us’; then the second line becomes an apposition to that object, or may be rendered as a subordinate clause, ‘whenever they/we fear him.’
The term mercy often implies not only a sympathetic consciousness of another’s situation but also a readiness and/or activity to help him in distress.
Those who fear him. For ‘to fear’ cf. above on v. 12, but in the specific use found here, and in 18.2, 4; 23.4, it is often better to render it by a verb meaning ‘to have respect/reverence for’ (as in Southern Subanen, Western Highland Purepecha, Navajo, Javanese, Tboli), cf. also, ‘to make great before oneself’ (Ngäbere). Kannada can employ a compound, ‘fear-devotion,’ that is in current use as a description of the life of piety; Apache renders the phrase by, ‘those-with-whom he-is-holy.’
From generation to generation, or, ‘from children to children’s children’ (Sranan Tongo), ‘descend-descending’ (a repetitive form, Bahasa Indonesia, Balinese), ‘life one-layer, life one-layer’ (Tae’), ‘from-those-who-have-been-being-born and-on to-those-who-will-be-being-born’ (Navajo); or, ‘forever’ (Vai, Western Highland Purepecha), ‘always’ (Bambara). Cf. also on v. 48.
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.