Look at the Law in Leviticus:
4:1-2
And the LORD spake unto Moses, saying, Speak unto the children of Israel, saying, If a soul shall sin through ignorance against any of the commandments of the LORD concerning things which ought not to be done, and shall do against any of them:
4:22-23
When a ruler hath sinned, and done somewhat through ignorance against any of the commandments of the LORD his God concerning things which should not be done, and is guilty; Or if his sin, wherein he hath sinned, come to his knowledge; he shall bring his offering, a kid of the goats, a male without blemish:
4:27-29
And if any one of the common people sin through ignorance, while he doeth somewhat against any of the commandments of the LORD concerning things which ought not to be done, and be guilty; Or if his sin, which he hath sinned, come to his knowledge: then he shall bring his offering, a kid of the goats, a female without blemish, for his sin which he hath sinned. And he shall lay his hand upon the head of the sin offering, and slay the sin offering in the place of the burnt offering.
51 And if a soul sin, and hear the voice of swearing, and is a witness, whether he hath seen or known of it ; if he do not utter it , then he shall bear his iniquity.
Leviticus 5
5:2-5
Or if a soul touch any unclean thing, whether it be a carcase of an unclean beast, or a carcase of unclean cattle, or the carcase of unclean creeping things, and if it be hidden from him; he also shall be unclean, and guilty. Or if he touch the uncleanness of man, whatsoever uncleanness it be that a man shall be defiled withal, and it be hid from him; when he knoweth of it , then he shall be guilty. Or if a soul swear, pronouncing with his lips to do evil, or to do good, whatsoever it be that a man shall pronounce with an oath, and it be hid from him; when he knoweth of it , then he shall be guilty in one of these. And it shall be, when he shall be guilty in one of these things , that he shall confess that he hath sinned in that thing :
5:14-19
And the LORD spake unto Moses, saying, If a soul commit a trespass, and sin through ignorance, in the holy things of the LORD; then he shall bring for his trespass unto the LORD a ram without blemish out of the flocks, with thy estimation by shekels of silver, after the shekel of the sanctuary, for a trespass offering: And he shall make amends for the harm that he hath done in the holy thing, and shall add the fifth part thereto, and give it unto the priest: and the priest shall make an atonement for him with the ram of the trespass offering, and it shall be forgiven him. And if a soul sin, and commit any of these things which are forbidden to be done by the commandments of the LORD; though he wist it not, yet is he guilty, and shall bear his iniquity. 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. It is a trespass offering: he hath certainly trespassed against the LORD.
Leviticus 6
6:1-5 And the LORD spake unto Moses, saying, If a soul sin, and commit a trespass against the LORD, and lie unto his neighbour in that which was delivered him to keep, or in fellowship, or in a thing taken away by violence, or hath deceived his neighbour; Or have found that which was lost, and lieth concerning it, and sweareth falsely; in any of all these that a man doeth, sinning therein: Then it shall be, because he hath sinned, and is guilty, that he shall restore that which he took violently away, or the thing which he hath deceitfully gotten, or that which was delivered him to keep, or the lost thing which he found, Or all that about which he hath sworn falsely; he shall even restore it in the principal, and shall add the fifth part more thereto, and
I'm not going to try to interpret the law, but it appears to me that sins done in ignorance are automatically covered by the blood sacrifice, while sins done knowingly must be repented of and restoration made.
IMO, willful sin is to sin with the knowledge that it is a sin. For example, since we have been taught and know that the commandment is that we should love our enemies and we choose to not love our enemies when they strike at us, then this is willful sin, imo. In order to obtain forgiveness, it must be repented of.
Peace,
Layla