Exegesis:

idou ‘behold,’ cf. on v. 20, here emphasizes the explanatory character of the following clause; hence renderings like “I tell you” (New English Bible), “why” (Williams), vois tu (Bible de Jérusalem).

gar ‘for,’ introduces the explanation of what Elizabeth said in the two preceding verses.

hōs egeneto hē phōnē tou aspasmou sou eis ta ōta mou ‘when the sound of your greeting came to my ears.’

egeneto … eis ta ōta mou ‘came to my ears’; the expression is rather colourless.

hē phōnē tou aspasmou sou ‘the sound of your greeting’; phōnē ‘sound’ or ‘voice’ is added here in order to show that the reference is not to the contents of Mary’s word of greeting, but merely to its sound.

en agalliasei ‘in exultation,’ cf. on v. 14. Both the substantive agalliasis and the verb agalliaomai often denote an exultation which is due to the Holy Spirit, cf. 10.21, 1 Pet. 4.13f.

eskirtēsen … to brephos en tē koilia mou, see on v. 41.

Translation:

When the voice of your greeting came to my ears, preferably, ‘when the sound of your greeting came to (or, fell-on/reached/called-in) my ear(s)’; or with further adaptations needed, ‘as-soon-as your well wishing resounded in my ear’ (Balinese, using an onomatopoeic verb suggesting the concept sound, similarly New English Bible), ‘when I heard your voice that greeted me.’

Leaped for joy. The verb usually can be rendered as in v. 41, but in some cases differentiation is needed, e.g. because of the adverbial qualification. For joy, or, ‘because of its joy,’ ‘because it rejoiced (or, exulted/was happy).’

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.