Unless I am reading this wrong, Judas Iscariot was not a believer but a thief who had a love for money for why he had betrayed Him.
John 6:62 What and if ye shall see the Son of man ascend up where he was before? 63 It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, they are spirit, and they are life. 64 But there are some of you that believe not. For Jesus knew from the beginning who they were that believed not, and who should betray him...
68 Then Simon Peter answered him, Lord, to whom shall we go? thou hast the words of eternal life. 69 And we believe and are sure that thou art that Christ, the Son of the living God. 70 Jesus answered them, Have not I chosen you twelve, and one of you is a devil? 71 He spake of Judas Iscariot the son of Simon: for he it was that should betray him, being one of the twelve.
John 12:4 Then saith one of his disciples, Judas Iscariot, Simon's son, which should betray him, 5 Why was not this ointment sold for three hundred pence, and given to the poor? 6 This he said, not that he cared for the poor; but because he was a thief, and had the bag, and bare what was put therein.
I suppose one could say that the scripture only referred to Judas as the traitor and that he could be a believer, and although scripture never testified of Judas Iscariot being a believer, Jesus did say this;
Matthew 6:24 No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon.
This is why I am discerning that Judas Iscariot was never a believer.
If you compare 1 Corinthians 3:10-17 at this link in the KJV
Bible Gateway passage: 1 Corinthians 3:10-17 - King James Version with Hebrews 6:1-8 in context, you would see the burning of the weeds as burning off of hat foundation all that denies Him but the foundation remains for why that spirit is saved even though the physical body will be destroyed i.e. physical death.
In context, the reason it is conveyed that it is impossible was to point out all those things a saved believer went through at the beginning, bears no repeating because he is still saved, but that there is only going on to perfection in living a life of repentance by laying aside every weight & sin daily by looking to Jesus Christ to help us get rid of the weeds and any works of iniquity off of that foundation & keeping it off by the grace of God.
Hebrews 6:1
Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection;
not laying again the foundation of repentance from dead works, and of faith toward God, 2 Of the doctrine of baptisms, and of laying on of hands, and of resurrection of the dead, and of eternal judgment. 3 And this will we do, if God permit.
4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, 5 And have tasted the good word of God, and the powers of the world to come, 6 If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame. 7 For the earth which drinketh in the rain that cometh oft upon it, and bringeth forth herbs meet for them by whom it is dressed, receiveth blessing from God: 8 But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned.