# to do their service

The word "service," an abstract noun, can be expressed as a verb. AT: "to serve" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])

# before Aaron and before Aaron's sons

"in the presence of Aaron and his sons"

# This was

"What they did was"

# They treated all the Levites in this way

"They did to the Levites what Yahweh commanded." The word "They" refers to the people of Israel.