How do we know that Christ's sacrifice is sufficient?

The sufficiency of Christ’s sacrifice is grounded in the New Testament's teachings. Unlike the repeated sacrifices of the Old Testament, which served only as a reminder of sin (Hebrews 10:3), Christ's one-time sacrifice is said to have perfected forever those who are sanctified (Hebrews 10:14). His work is described as complete and effective, as indicated when He proclaimed 'It is finished' (John 19:30), signifying that all necessary conditions for salvation had been met. Thus, believers can have assurance that there is no further sacrifice needed, as seen in Hebrews 10:17-18, where it clarifies that where remission of these is, there is no more offering for sin.