For … therefore: Judith is saying that she proposes the following scheme because she is a religious woman. The logical relationship is only implied in Good News Translation. If one were to insert “So here is what I will do” or “So here is my plan” between the two sentences of Good News Translation, the proper relationship would be explicit.
Your servant is religious: See the previous verse for a comment on servant. In some languages it will be natural style to say “I, your servant, am a woman who obeys God’s laws.”
Serves the God of heaven day and night: Good News Translation has “I worship the God of heaven day and night.” “Worship” is misleading if it suggests a formal activity such as attending a religious service or constantly doing such an act that most people perform on occasion. The verb used here is related to the noun used often in the book to describe Holofernes’ personal servants, those who attend him and wait on him (for example, 10.20; 11.20) With this verb she describes herself as a servant of God, one who is ready at his call at all times, ready to do his will. On the use of the term God of heaven in Judith, see the note on 5.7-8. Judith here is subtly letting Holofernes know that she does not intend to be the servant of Nebuchadnezzar (verses 1, 4), but instead presents herself as one with prophetic powers, one whom Holofernes must accommodate in order to win the victory she promises. This clause along with the previous one may be rendered “I am a religious woman, ready to serve the God of heaven day and night” or “I carefully obey the laws of the God who lives in heaven and am ready to serve him day and night.”
I will remain with you: Good News Translation has “I will stay here in your camp.” In approaching this sentence the translator must decide whether Judith intends a subtle seduction by her choice of words. She says literally “I will stay with you [singular].” If there is none at all, “I will stay here in your camp” reflects the Greek text well; the word “camp” does not appear, but the preposition used in with you allows that interpretation. “I will stay in camp with you” or “I will stay in camp near you” might express well both Judith’s actual plan and what Holofernes wants to hear her saying.
Every night your servant will go out into the valley, and I will pray to God: In 12.7-9, where Judith carries out these plans, she bathes each night while in the valley, apparently as part of a purifying ritual. She does not mention that here. She must not give the Assyrians reason to come spying on her, and she must not risk insulting them by insinuating that she must purify herself after being around them.
When they have committed their sins: They refers to the Israelites, the people of Bethulia; by their sins Judith is referring to the matters in verses 12-13.
Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Judith. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here.