We know Jesus is able to save because He possesses the necessary qualifications: He is God, a near kinsman, and without sin.
The ability of Jesus to save is grounded in His qualifications as our Savior. First, He is a near kinsman, which means that He shares in our humanity and can represent us before God. Second, He is a mighty man of wealth, possessing the infinite resources of grace and mercy needed to redeem us from our sins. Lastly, His sinless nature and divine identity ensure that His sacrifice is sufficient to cover the penalty for our sin. As Hebrews 10:14 tells us, by one offering He has perfected forever those who are being sanctified, reinforcing His ability to save completely and utterly what has been lost.
Scripture References:
Hebrews 10:14, Matthew 9:27-29, Genesis 3:15, John 14:6
Commentary