Only once and with consequences

Jesus told his disciples that he will return only once and that when he does, after a time of great tribulation, it will be visible to everyone and be followed by immediate and dire consequences for those unprepared and for those who were adversaries of God.

A Book to trust #11 Archaeology confirming or denying claims of the Bible #2 New Testament

For matters that happened in the first century of our common era historians of the first century like Tacitus, Josephus and later ancient writers like Africanus provided enough material to go and further Alexandrian manuscripts, findings from the Qumram caves and research from contemporary archaeologists and historians like Blomberg, Henry, Scott, Tabor, Droge, Ramsay, Samuelsson and many others.