“For all the promises of God find their Yes in him. That is why it is through him that we utter our Amen to God for His glory.” - 2 Corinthians 1:20
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The birth of Christ was the fulfilling of ancient promises. God had long spoken of a Redeemer to come, and now every word was made good. The covenant made with Abraham, the promise given to David, the visions of the prophets, all meet together in Christ. Not one word has failed. Simeon waited for the consolation of Israel because He believed the promise. And when He took Christ in His arms, He took the promise itself. He needed no further proof. He desired no further sign. He had Christ, and having Christ He had all. So will every believer find that when He has Christ, He has the substance of every promise. Christ is the covenant in whom all blessings are conveyed.
Let us mark that the promises of God are not uncertain or unstable. They are not built upon the worthiness of man, but upon the truth of God. Generations passed away, empires rose and fell, yet the promise of God stood firm until the appointed time. The faithfulness of God is the foundation of the believer’s hope. The same God who kept His promise in sending Christ will keep all His promises to those who trust in Christ. As surely as Christ came the first time, so surely will He come again. The believer may wait with confidence for the perfect salvation that the Redeemer has purchased.
The sight of Christ warms and satisfies the heart of the believer. To behold Him by faith is to behold the mercy, faithfulness, and salvation of God. Simeon was content to depart in peace because He had seen Christ. If we would have peace in life and peace in death, we must embrace Christ as our salvation. Nothing else can quiet the conscience or satisfy the soul. In Him the promises are yes and amen.
(Taken From Matthew Henry's Commentary on Luke)