The oldest written document of the New Testament is 1 Thessalonians. It gives us the oldest foundational principles of the church. 1 Thessalonians begins by turning the clock back to remember how the gospel saves and changes pagans.
One of the themes in the prophets is their call of exhortation to God’s people. The call can be to get back to Torah observance, or justice or it in case of Haggai to stop procrastinating. We get to learn from how God shepherds His people during periods of “we will do it later” and gain wisdom for our own tendencies.