How do we know Christ's atonement was sufficient?

The sufficiency of Christ's atonement is assured through His own declaration that 'It is finished' on the cross (John 19:30). This statement signifies that He successfully fulfilled the sacrificial requirements by bearing the sins of His people. The permanence of His sacrifice is emphasized in Hebrews 10:14, which states that by one offering, He has perfected forever those who are being sanctified. Thus, Christ's atonement is not only sufficient but effective for all those He came to redeem.