For they eat the sacrifices to the Lord: They refers to the priests. Good News Translation is good here. We could also say “Food that people offer as sacrifices to the Lord is what the priests eat.”

Which he gave to him and his descendants: Good News Translation again is good, although we could add to it by saying “The Lord gave this right to Aaron and his descendants.”

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.