Hebrews 6:4-6 (New International Version)
4It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, 5who have tasted the goodness of the word of God and the powers of the coming age, 6if they fall away, to be brought back to repentance, because to their loss they are crucifying the Son of God all over again and subjecting him to public disgrace.
The above passage of Scripture has caused many to fear and to be in bondage. Many Christians believe as such when they have sinned greatly and are lost , making it is impossible to come back. Below are short explanations for each part. It is helpful to note that the letter to the Hebrews is written to Jews and not Gentiles. As such any warnings which are issued are issued to them and not the Gentiles. Let us consider their story in Numbers and Deuteronomy.
The Hebrews stood at the entrance of God’s physical rest –the Promised Land. This was after they witnessed the column of cloud in the day and bright fire in the night; the brightness of His glory on Mount Sinai; and the fire that consumed the rebels. The Hebrews saw His light –they were “enlightened”. (Exodus 13: 21-22, 2 Samuel 22: 7-13, Numbers 11: 1-3)
They ate the daily bread –the manna– that He provided. The Hebrews tasted the food (“heavenly gift”) given from heaven to know about the word of God (Exodus 16: 11-18, 31, Deuteronomy 8: 1-4).The Holy Spirit that rested on Moses (so that he could fairly judge the disputes of the people) was later partaken (shared) with seventy leaders to help carrying the heavy burden. In this way, the people partook (shared) in the Holy Spirit (Numbers 11: 4-6, 10-17).
They saw supernatural events occur before their eyes –like the sea parting before them so they could escape from slavery and their enemies be destroyed (Exodus 14: 21-28). Those miracles were physical demonstrations of spiritual power yet to come through Jesus.
But even after all of these, those stubborn people deliberately refused to go into the Land –God’s Promised Land of rest. That is what it means “by sinning wilfully” or “keep on sinning” by constantly rejected Jesus as their Messiah. Hence please note it is written towards the unbelieving Jews. It is not a letter written to Jews or Gentiles who already believed. The promises which however which are made are available for the believer upon his belief. Therefore it does not talk about a believer that has gone away. It is possible to come back. The Father of the Prodigal Son proves that!