Exegesis:
kai ethento … en tē kardia autōn ‘and (they) laid to heart’; the phrase is best understood in the light of the Hebrew expression sim belev ‘to lay to heart,’ ‘to pay heed to.’ The subsequent clause indicates that the expression here refers to the astonishment caused by the birth of the child of Zechariah and Elizabeth.
ti ara to paidion touto estai ‘what then will this child be.’ ara serves here to enliven the question. The question is rhetorical, i.e. no direct answer is given or expected, although the question itself more or less suggests an answer.
kai gar cheir kuriou ēn met’ autou ‘for indeed the hand of the Lord was with him,’ in order to help him or to stand by him.
kai gar, stronger than the sole gar, an elliptic phrase, either as “for besides all that” (Plummer, Klostermann), or, as “for indeed” (New English Bible, Bible de Jérusalem), preferably the latter.
cheir kuriou ‘the hand of the Lord’ i.e. the saving and helping power of the Lord.
einai met’ autou ‘to be with him.’
Translation:
All who heard them. The pronoun “them”, here and in the next clause, refers to “these things” (v. 65), i.e. the events told in the preceding narrative, cf. “the whole matter” (Phillips); in some languages idiom requires a reference to the talking heard (cf. on v. 41), e.g. ‘all who heard people speak about them, or, heard the talk about that whole matter.’
Laid them up in their hearts. Many languages have formally similar expressions, but that does not warrant their referring to the same state of mind. Toraja-Sa’dan, for instance, possesses three comparable expressions, (1) ‘put-into the stomach (inward being),’ equivalent to the English ‘lay to heart’; (2) ‘put-into the spirit/mind,’ i.e. ‘consider’; and (3) ‘put-into the breast,’ i.e. ‘feel offended.’ Some other idioms used are, ‘engraved in their heart’ (Bible de Jérusalem), ‘noted-down in their heart’ (Sundanese).
What then will this child be, or “become” (New English Bible, also many other versions), or, ‘whoever will this child become,’ an idiom suggesting that the child will be someone great (Marathi, where a comparable idiom, ‘how will this child turn out,’ would suggest a reference to a naughty boy), ‘then what will that infant be(come) in the future’ (Thai, where a shorter idiom ‘what will that infant become,’ would be used when referring to disease or infirmity that may be in store for the child).
The hand of the Lord was with him is usually to be rendered by another metaphorical expression, such as ‘he was sheltered by the hand of the Lord’ (Javanese), ‘the Lord carried him on the palm of his hand’ (Toraja-Sa’dan), ‘the eye of God was always on him’ (Tboli, a figurative expression used of a possession one values highly, or a person one loves dearly); or non-metaphorically, e.g. ‘the Lord helped him’ (South Bolivian Quechua, Kituba). Most of the renderings of ‘to be with’ are different from those in v. 28, one of the reasons being that expressions used there with a personal subject cannot go with ‘hand’ or ‘power.’ Medumba uses a compound pronoun indicating individual dual (cf. on v. 58): ‘the hand of the Lord was he-plus-he.’
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.