How do we know Christ's work is enough for our salvation?

We can be assured of Christ's sufficiency for salvation through the teaching of Scripture, particularly the prophecies found in Isaiah. Isaiah 40:2 explicitly states that our warfare is accomplished and our iniquities are pardoned. This demonstrates that the battles we think we fight for our own salvation are ultimately unnecessary, as Christ has already secured the victory. The very nature of grace is that it is unearned and cannot be supplemented by our works. If God has declared us justified based on Christ's sacrifice, we can trust that it is not only enough but perfectly sufficient to secure our standing before Him for eternity.