Exegesis:

to gar hagion pneuma didaxei humas … ha dei eipein ‘for the Holy Spirit will instruct you what you must say,’ i.e. the Holy Spirit will put the right words in your mind and mouth.

en autē tē hōra ‘at that very hour, or, moment,’ cf. on 10.21 and reference there.

Translation:

In that very hour may be given a more emphatic position, cf. e.g. “for when the time/moment comes, the Holy Spirit…” (New English Bible, The Four Gospels – a New Translation).

What you ought to say, or, “what is the right thing for you to say” (Phillips), or simply, ‘the suitable word(s).’

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.