The opening words in Greek express an emphatic contrast between the practice of Tobit and the practice of all his relatives. In English this is rendered as but in most versions.

I kept myself is literally “I kept my soul,” a translation into Greek of a Hebrew idiom, meaning “I would not allow myself.” For this verse Good News Translation has “but I refused to do so,” while Contemporary English Version makes it clear that it was not permitted by the Law of Moses: “But I decided to eat only what was allowed by the Law of Moses.”

Quoted with permission from Bullard, Roger A. and Hatton, Howard A. A Handbook on Tobit. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here.