Why is the church not part of the tribulation?
The church is not part of the tribulation because that period is God's dealing with the nation of Israel. The church is not under Israel's covenants; those covenants are Jew-only and have nothing to do with Gentiles, so the church cannot be run into God's covenant dealings with Israel.
Les explains that the tribulation is primarily God dealing with the nation of Israel, so you cannot run the church into God's dealing with His covenant people. The church is not under any of those covenants; they have nothing to do with the Gentile, because they are Jew only. Those covenants will finally come into fruition in the tribulation, the time of God dealing with Israel. He cites Jeremiah 30:5, where the voice is trembling, fear, and not peace, and describes the horrible events coming on the earth, centered in the Middle East and directed primarily to the children of Israel.
For thus saith the LORD; We have heard a voice of trembling, of fear, and not of peace.
More Questions
Why should the church not be mixed with Israel in the tribulation?
The church cannot be allowed to mix with Israel during the tribulation, because the tribulation is God's dealing with Israel, not the church.