He is to bring to the priest an unblemished ram of proper value from the flock as a guilt offering. Then the priest will make atonement on his behalf for the wrong he has committed in ignorance, and he will be forgiven.
KJV
And he shall bring a ram without blemish out of the flock, with thy estimation, for a trespass offering, unto the priest: and the priest shall make an atonement for him concerning his ignorance wherein he erred and wist [it] not, and it shall be forgiven him.
ASV
And he shall bring a ram without blemish out of the flock, according to thy estimation, for a trespass-offering, unto the priest; and the priest shall make atonement for him concerning the thing wherein he erred unwittingly and knew it not, and he shall be forgiven.