God gave to Abraham the promise of salvation, and this promise was to be received by faith. Later He gave to Moses the law which, when obeyed, promised blessings to the Jews. God's covenants with men were sealed by the blood of animals, and transgression of the covenants were forgiven through the blood offering for sins. And then God sent Jesus, and made a New Covenant of salvation with Him, sealed in His own blood. This covenant is eternal because Jesus is not only man, but God.
Nothing can nullify it and no other promise of salvation can add to it.
In this New Covenant, Jesus could be seen as the object of faith and the fulfillment of the law. Here was the promised One, the descendent of Abraham. Now all of God's promises were accomplished. These promises would make God's finished salvation in Christ invalid, something the law given to Moses never did. In contrast, the Lady of Fatima promised salvation to those who embrace devotion to her Immaculate Heart, and implied that Jesus backs her promise.