So then links the quotation in a general way with what has gone before: “You are God’s people, if you keep up your courage. So then, listen when God (or Christ) speaks to you in this psalm.” It is grammatically possible to link So then with particular verbs, either (a) do not be stubborn in verse 8, or even (b) be careful in verse 12. Choice (b) would in effect put the entire quotation in parentheses and is very artificial. Good News Translation‘s general So then, indicating a new step in the argument, is probably best. An equivalent of So then may be a phrase meaning “Therefore,” “In view of all this,” or even “As a result of what has been said.”
Mention of the Holy Spirit would lead the original readers of Hebrews to expect a quotation from Scripture; ancient Jewish teachers often introduced quotations from the Old Testament in this way. However, modern readers may need to be told more clearly that a quotation is about to begin (Biblia Dios Habla Hoy “as the Holy Spirit says in Scripture”), or even that the Holy Spirit is God’s Spirit (Die Bibel im heutigen Deutsch first edition “God says through his Spirit”).
Is the correct translation If or “when” (Moffatt, Revised Standard Version)? The Greek word usually means If, but sometimes, as in John 12.32; 14.3; and 1 John 2.28, it is virtually equal to “when.” Here the question is not whether people will hear God’s voice (since God is speaking or is about to speak in this very passage), but whether, when people have heard his voice, they will obey it. New American Bible‘s “if you should hear his voice” is too indefinite, and “when” is more likely in this context. Some translations (Barclay, Translator’s New Testament; compare Jerusalem Bible) omit both “if” and “when,” and translate hear as “listen to.” Hear can mean “listen to,” as it usually does in commands. Here Barclay has “Today I plead with you, listen to his voice.” Good News Translation‘s construction is better, since it throws weight onto the first main verb of the quotation, do not be stubborn.
To speak about “hearing someone’s voice” may be heavy or repetitive in some languages. Jerusalem Bible has simply “listen to him.” Another possibility is “when you hear me speaking (to you).”
A literal rendering of If you hear God’s voice today could mean merely hearing the voice of God but not hearing the message that is actually said. It may be better, therefore, to translate the conditional clause as “When you hear what God is saying today.”
Quoted with permission from Ellingworth, Paul and Nida, Eugene A. A Handbook on The Letter of the Hebrews. (UBS Handbook Series). New York: UBS, 1983. For this and other handbooks for translators see here .