1 Thess 4:13-18
13 But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
14 For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
18 Wherefore comfort one another with these words.

Those that are saved, their fleshly bodies will be changed into an immortal body, not needing food nor drink, not needing sleep or air to breathe. Nothing in this universe would harm or hurt them. We could walk on the surface of the sun, or play checkers on Pluto. Extreme temperatures would have no effect on us.

Just like any plane or train ticket, if you are not careful, you can lose the ticket and not be able to get on board. Do not believe the false teachers that say “once saved always saved”. That is a lie, the same as the lie told by the serpent, “You will not surely die”. Yeshua also said the following: