Thank you for the question on faith, “Why would God give people direct proof in a Millennium Reign after The Return if this entire reality is based on faith for salvation?”
Here are some thoughts for one’s consideration:
A. Faith is based on a promise given by God to his people.
Hebrews 11 says this, “Now faith is confidence in what we hope for and assurance about what we do not see.” (NIV). Christian have confidence in the promises of God based on the character of God that he is holy, righteous, and faithful. In other words, God doesn’t lie when he makes a promise.
B. The promise by God has a fulfillment time frame.
Depending on the promises of God, the fulfillment may be in days, months, years or longer. God declared that Israel will go into captivity for 70 years and then they will return. King Nebuchadnezzar destroy the Temple in 586 BCE where as Cyrus I allowed the exiled people to return to their homeland.
If a promise is indefinite in being fulfilled or never fulfilled, then would question the character and the word of the person. If a person promises to repay back a loan in one year, one believes it. There is a deadline. Failure to fulfill that promise would cast doubt on the person’s words and character.
The proof or the existence of the Millennial Kingdom is the fulfillment to the Jewish people that a person from the lineage of King David will sit on the throne and bring about a peace for Israel and for the world. Faith is not just forever wishing. Faith has an end date when it becomes a reality.
Salvation is instantaneous for the one who believes. The full reality of that faith comes upon the return of Jesus Christ when the dead in Christ will rise to life and those who are alive will be caught up with the resurrected dead to be with the Lord forever. The reunion of our loved one in heaven who believes in Jesus is a promise that one day will be fulfilled. Believers will be present in the Millennial Kingdom as Christ rules as King of Kings and Lord of Lords. That is our ultimate hope and believers believe this is true based on the promise of God.
SUMMARY: Faith has an end date.