John Gill Commentary Leviticus 4:14

"when the sin wherein they have sinned is known, then the assembly shall offer a young bullock for a sin-offering, and bring it before the tent of meeting." — Leviticus 4:14 (ASV)

When the sin which they have sinned against it
Any of the commandments of the Lord forbidding such a thing to be done:

is known ;
is made known to them by the priest, or any other, so that they are convinced that what has been done is wrong, though done through ignorance:

then the congregation shall offer a young bullock for the sin, and
bring him before the tabernacle of the congregation ;
the same offering with that of the anointed priest, he being, as Aben Ezra on the place observes, equal to all Israel.