Returning to Judaism, after being saved and filled with the Spirit, because of pressure from friends and family members who do not believe, or being threatened with death, means you depart from Christ and renounce Him as a false teacher and false messiah.
Surely you understand this puts Christ to an open shame, in which the person who does this can not be brought back to repentance.
For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame.
Hebrews 6:4-6
All throughout the dark ages and even today in third world countries, people have suffered greatly as martyrs, refusing to renounce Jesus Christ as Lord, while enduring torture being faithful to the end, because they know the truth about what happens to those who depart from Christ under persecution.
“Then they will deliver you up to tribulation and kill you, and you will be hated by all nations for My name’s sake. And then many will be offended, will betray one another, and will hate one another. Then many false prophets will rise up and deceive many. And because lawlessness will abound, the love of many will grow cold. But he who endures to the end shall be saved. Matthew 24:9-13
JLB