Exegesis:

en tō genesthai tēn phōnēn lit. ‘after the voice had happened i.e. spoken,’ cf. Revised Standard Version.

heurethē Iēsous monos ‘Jesus was found (to be) alone,’ i.e. ‘they (i.e. the three disciples) saw that Jesus was alone,’ implying that the others had gone (cf. Phillips).

kai autoi esigēsan ‘and they kept silence.’

sigaō ‘to be silent,’ ‘to keep silence.’

oudeni apēggeilan … ouden hōn heōrakan ‘they told nobody anything of what they had seen.’ The two negatives reinforce one another.

en ekeinais tais hēmerais ‘in those days,’ probably referring to the time that Jesus was with them.

Translation:

When the voice had spoken, or, ‘had-sounded’ (Tae’). The rendering should preferably echo the one of “a voice came” in v. 35.

Jesus was found alone. For the verb cf. on 7.10; for “Jesus … alone”, i.e. no one but Jesus.

They, or, “the disciples”, ‘the three’ (Malay, Toraja-Sa’dan), or again specification by a deictic element.

Kept silence. If an object is obligatory one may transpose the phrase ‘what they had seen,’ e.g. ‘the disciples kept-silent-about the things they had seen’ (Balinese), or insert a generic object, e.g. ‘they kept silence about it, or, the event.’ Some versions shift to ‘kept-it-secret’ (Bahasa Indonesia RC), an acceptable means to avoid tautology in languages where the renderings of ‘to keep silent’ and ‘not to tell, or speak’ coincide or closely resemble each other.

Told no one … anything. Other ways to express the strong negation are, ‘told no single person … a word,’ ‘told people … entirely nothing,’ etc.

For one possible transposition of what they had seen see above; another that may be necessary is, ‘the disciples who had seen all this kept silence (about it) and told no one of it….’

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.