“In hope of eternal life, which God…promised before the world began” (Titus 1:2).
In the Law of Moses, God promised the people of Israel that they could “live” (Lev. 18:5)—live eternally—if they kept His commandments. We know that’s what Leviticus 18:5 meant because the Lord Jesus quoted that verse to a Jewish man seeking eternal life (Lu. 10:25-28).
But God promised us Gentiles eternal life before the Law, even “before the world began.” But unlike the promise of life He made to the Jews in the Law, He didn’t reveal His promise to us Gentiles for thousands of years! Speaking of that promise (Titus 1:2), Paul added,
“But hath in due times manifested His word through preaching, which is committed unto me…” (Titus 1:3).
When God finally decided to reveal His promise to give the Gentiles eternal life, He “manifested” it through Paul.
If you’re not sure what that word “manifested” means, it is well defined in something the Lord said about things that had not yet been revealed about God’s prophetic program for Israel:
“…nothing is secret, that shall not be made manifest, neither any thing hid, that shall not be known…” (Luke 8:17).
So to make something manifest means to make known something that was secret or hidden. That means when Paul says that God “manifested His word through preaching, which is committed unto me,” he meant that he preached a secret that had been hid but now was made known.
Paul wasn’t just called on to reveal the mystery that God promised eternal life to Gentiles before the world began. He was called on to reveal the fellowship of the mystery, something he explained a few verses earlier in that passage when he said,
“…God…made known unto me the mystery…that the Gentiles should be fellowheirs and of the same body…” (Ephesians 3:2-6).
The fellowship of the mystery is that Gentiles could not only have eternal life, they could be fellow or equal* members of “the same body,” the Body of Christ, with Jewish believers. And Paul was raised up to make this equality manifest.
In the 19th century, many Americans believed that it was the “manifest destiny” of the United States that our nation would expand across North America. But in the 1st century, the Apostle Paul made it manifest that even Gentiles like us are destined to live eternally as equal heirs with Jewish believers in the Body of Christ for all eternity. Glory! source