The expanded translation in the first sentence of Good News Bible brings out the negative and positive aspects of the Greek word that Revised Standard Version translates literally Cleanse out.
The first part of this verse brings out the moral of verse 6b. Translators may link the two verses by adding “so”; for example, “So you must remove the old yeast.” Paul uses language drawn from Exo 13.7 and perhaps Exo 12.3-21, which describes the basis of the Jewish Passover feast. The custom was (and still is) to clear out all yeast from Jewish houses before people celebrated the Passover. Paul is applying this custom to people’s behavior, so Good News Bible is right to add “of sin.” Good News Bible anticipates verse 8 in order to explain this language to non-Jewish readers of this translation. Translators may need to use a simile; for example, “take out the sin which is like old yeast.”
The difference between Revised Standard Version and Good News Bible is that Revised Standard Version translates the Greek metaphor literally, whereas Good News Bible has replaced it with a simile. Leaven equals sin, and the phrase Cleanse … that you may be a new lump means “Cleanse yourselves from sin so that you may be pure.” Paul is making a spiritual application here. As with modern English, many translators will find it difficult to maintain the metaphor here.
The clause that you may be a new lump may be expressed as “that you may become a people who are completely new.” The word new translates a Greek word often used of “fresh” food. Good News Bible has expanded the text to make its meaning clear, yet nothing has been added to the meaning of the Greek.
The word For before the clause Christ, our paschal lamb … introduces a different thought. Die Bibel im heutigen Deutsch makes this transition even clearer: “And so you are, since Christ our Passover lamb was sacrificed.” The sacrifice of the lamb was central to Passover, as Good News Bible‘s expanded translation shows. The verb has been sacrificed refers to a single event in the past, so a translation like New English Bible‘s “our Passover has begun…” is misleading; Revised English Bible has “has been sacrificed.” However, New English Bible brings out better than Revised Standard Version or Good News Bible the fact that “Christ” is emphatic in the Greek: “… the sacrifice is offered—Christ himself.” Another possible translation is “Christ was sacrificed as our Passover lamb,” or in languages that do not normally use the passive one may say, for example, “they have sacrificed Christ.” The “Passover” was the Jewish festival when the Jews remembered how God had delivered them from Egypt. Many languages simply transliterate the English or Latin terms. However, in other languages “Passover” will be rendered as “Feast/Festival to Remember the Passing Over,” “Feast of the Deliverance,” or even “Festival of the Time when the Angel Passed Over.” In such cases this final sentence will be rendered as “For Christ, our lamb for the Festival to Remember the Passing Over has been sacrificed,” or “For they have sacrificed Christ, who is the lamb for our Feast of the Deliverance.”
Quoted with permission from Ellingworth, Paul and Hatton, Howard A. A Handbook on Paul’s First Letter to the Corinthians, 2nd edition. (UBS Handbook Series). New York: UBS, 1985/1994. For this and other handbooks for translators see here .