It is what Jesus said. It's part of His Revelation to His churches. You don't offer any proof that the beast does not need to first ascend out of the abyss before it can make war against the saints and overcome them.
Revelation 17:8
The beast that you saw was, and is not, and is about to ascend out of the abyss and go into perdition. And those dwelling on the earth will marvel, those whose names were not written in the Book of Life from the foundation of the world, when they behold the beast that was, and is not, and yet is.
Revelation 13:3
And I saw one of its heads as having been slain to death, and its deadly wound was healed. And all the earth marveled after the beast.
Revelation 13:7
And it was given to it to war with the saints and to overcome them. And authority was given to it over every tribe and tongue and nation.
Revelation 11:7
And when they complete their testimony, the beast coming up out of the abyss will make war against them and will overcome them and kill them.
Matthew 24:9
Then they will deliver you up to be afflicted and will kill you. And you will be hated of all nations for My name's sake.
Remember that the above verses are talking about a Great Tribulation that results in the Lord's return when He returns "immediately after" the tribulation of those days (Matthew 24:29) - not the tribulation to be suffered by all Christians at various times throughout the gospel Age.