Exegesis:

egeneto nephelē episkiazousa ‘there came a cloud, overshadowing,’ ‘there appeared a cloud, covering’: it is generally agreed that egeneto ‘came,’ ‘appeared’ here has an independent force of its own and does not function as an auxiliary to episkiazō ‘overshadow’ (as Revised Standard Version translates it): cf. American Standard Version, The Modern Speech New Testament, Moffatt, Goodspeed, Manson, Translator’s New Testament, Le Nouveau Testament. Version Synodale, Zürcher Bibel.

nephelē (13.36; 14.62) ‘cloud.’

episkiazō (only here in Mark) ‘overshadow’ (from skia ‘shadow’), ‘cover.’

houtos estin ho huios mou ho agapētos ‘this is my Son, the Beloved’: cf. the Voice from Heaven at the baptism of Jesus, 1.11. Notice that at the baptism the Voice addresses itself to Jesus; here, to the disciples.

Translation:

Overshadowed may be rendered as ‘passed over them,’ ‘came between them and the sun’ or ‘covered up the sun for them.’

As noted in Mark 1.3 in some languages one cannot speak of a ‘voice speaking,’ much less one ‘coming out of a cloud,’ as in this verse. People may speak, but not ‘voices come.’ In Central Tarahumara, for example, the only way to translate this passage is to say ‘God spoke out of the cloud.’ Some translators have tried to make the reference less specific by rendering the passage as ‘they heard someone speaking in the cloud,’ but this suggested a person, not God. In certain instances, however, it is possible to say ‘they heard words coming from somewhere in the cloud’ (cf. Indonesian and Javanese ‘and a voice out of the cloud was heard’), a rendering which conserves something of the indefinite form of the original.

For my beloved Son see 1.11. In Navajo this phrase becomes ‘this is the Son I love,’ but it is nonrestrictive. That is to say, this passage must not be translated in such a way as to suggest that Jesus is the Son God loves, while other sons he does not love. The correct meaning may be conveyed in some languages by translating ‘this is my Son; I love him.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .