Q - How do we know that the Rapture will happen before the start of the Tribulation?

A - We have to look at the Bible as a completed work. You can't base your beliefs on just one verse or chapter in the Bible.

All through the Bible we learn who God is, how he thinks, and how he does things.

God himself teaches that he never changes he is the same today tomorrow and for evermore.

So if we know what God did in the past we can know without any dough what he will do in the future.

Over the past 6000 years God has never sent any wrath on his own people. He will never do this in the future because he would have to change to anything different and God never changes.

He has never sent his wrath without first giving warning. And He never will because again he would have to change.

The Bible says God is a fair and Just God and all throughout the Bible we see that this is true. So God cannot send any wrath on his own people because that would be unfair and God cannot be unfair, and there's no reason for him to make his true believers suffer the tribulations that would be pointless and he will not do that.

There are those that teach God will not remove his people however he will protect us from the tribulations he sends. This is an insane belief and it won't happen people, READ THE BIBLE.

Jude 14-15: ...Behold, the Lord came with many thousands of His holy ones, to execute judgment upon all, and to convict all the ungodly of all their ungodly deeds which they have done in an ungodly way, and of all the harsh things which ungodly sinners have spoken against Him.

The tribulation is for the ungodly not for true Christians. And the "overcomers" will be removed before God send any tribulation on this earth; you can take that to the bank.

Now as for the lukewarm Christians he may leave them and not take them in the Rapture just to find out if they are worthy of heaven.

I also know that God always rewards his believers for great faith in him, and I believe that the people that have a great faith in him and his word that the Rapture is going to happen (and very soon) and are ready and watching and praying for it will be rewarded for their faith by making them kings and rulers of all his goods in the millennial reign of Christ.