Then I remembered thy mercy, O Lord, and thy work from of old: In English “remembered how merciful you are” (Good News Translation) is a bit easier to understand than remembered thy mercy. With thy work from of old, the author speaks of all the ways the Lord had helped his people throughout their history. We may translate these two lines as “But then, Lord, I remembered how merciful you are and how you have helped your people in times past.”

That thou dost deliver those who wait for thee: Good News Translation clarifies this line by beginning a new sentence and repeating “I remembered.” Those who wait for thee means “those who patiently trust you” (so New English Bible). Good News Translation has “those who rely on you,” or we may say “those who trust you.”

And dost save them from the hand of their enemies: The hand of is simply a Hebrew idiom. It is often best for translators to leave it implied. The final two lines may be combined by saying “You rescue those who rely on [or, trust] you when their enemies attack them.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Sirach. (UBS Helps for Translators). New York: UBS, 2008. For this and other handbooks for translators see here.