because in those days there will be tribulation unlike anything that has happened from the beginning of the creation that God created until now, and it will absolutely not happen again. Bible see other translations

“such tribulation.” This is the time of “great tribulation” Jesus spoke of in Matthew 24:21. Jesus would have learned a lot about the Tribulation period from the Old Testament. This great tribulation is the subject of much of the book of Revelation, with its seven seals, seven trumpets, seven thunders, and seven bowls of judgment.

[For more on the prophecies of the Great Tribulation, see commentary on Isa. 13:9.]

Commentary for: Mark 13:19