What does the Bible say about willful sin?

Hebrews 10:26 explicitly states that if we willfully sin after we have received the knowledge of the truth, there remains no more sacrifice for sin. This does not imply that every Christian who sins willingly is lost; rather, it addresses those who, after accepting the gospel, deliberately turn away from the sufficiency of Christ's atonement. Such an act signifies a rejection of the only means of salvation, as they return to reliance on the Law, which cannot offer redemption, highlighting the seriousness of abandoning faith in Jesus.