To be mature Christians

Usually, the epistles in the New Testament were written to tackle some specific issues. For example, the first epistle to the Corinthians deals with a host of problems: division, resurrection, sexual immorality and married life etc. So what issues was the epistle to the Hebrews dealing with? It seems to be dealing with the question of Jesus' status in relation to angels.
Though a man, Jesus is superior to angels. The author of Hebrews was trying to defend challenges of the status of Jesus. Such challenges came from competing religious movements in the first century. Probably at that time, worship of angels was still popular. Angels had long been protectors of countries (Daniel 10:10-14; 12:1; Jeremiah 30:7 etc. Thank you Mr. John Fok, for his generosity to allow me to quote from his webpage). In Revelation, angels were even guardians of churches (Revelation 1:20-3:22).
OK, Jesus would work miracles. Even that was not powerful enough to qualify Jesus a local deity. At most, Jesus was only a faith healer, not to mention that he was a crucified criminal. For Christians who hold on to their faith in Jesus, it is important to show that Jesus is not just any son of God (a term referring to angels), but the Son of God. For Christians, Jesus was no mere faith healers. Yes, he was crucified in public, but he was not a criminal. Furthermore, God raised him from the dead and made him sitting on His right in heavens. Jesus was made perfect through his suffering (Hebrews 2:10, 5:9). Moreover, Christians were happy to have found a prooftext in Psalm to show that Jesus was begotten from God, not made by God (Hebrews 5:5; Psalm 2:7). After all, angels are just creatures made by God. They are not born from God.
The author of Hebrews also dealt with the status of Christians in relation to the Israelites. He proved again from Psalm that the Israelites had provoked the wrath of God. They had forfeited their inheritance right. Christians should work hard to replace them and enter into this God's rest which the Israelites had been banned because of their disobedience and lack of faith (Hebrews 3:16-19, 4:11). So far, so good.
Turning now to his readers, the author found that their faith was too rudimentary. They ought to be teachers, teaching the world the road to salvation. However, they were badly in need of the author to teach them again the first principles of God's word, probably because some of them had turned away from Jesus.
For though by this time you ought to be teachers, you need some one to teach you again the first principles of God's word. You need milk, not solid food;
for every one who lives on milk is unskilled in the word of righteousness, for he is a child.
But solid food is for the mature, for those who have their faculties trained by practice to distinguish good from evil. (Hebrews 5:12-14).
The word of God is the word of righteousness. His readers were children that lived on milk. They needed to become mature Christians capable of distinguishing good from evil. So, the first principle of God's word is to distinguish good from evil. Mature Christians are those who can do so.
Therefore let us leave the elementary doctrine of Christ and go on to maturity, not laying again a foundation of repentance from dead works and of faith toward God,
with instruction about ablutions, the laying on of hands, the resurrection of the dead, and eternal judgment (Hebrews 6:1-2).
So, repentance, faith, liturgy, resurrection and last judgment are elementary doctrines of Christ. The author of Hebrews advised us to proceed towards maturity.
What qualities do mature Christians have? What happened to those who gave up their faith and turned away? From a negative point of view, the author of Hebrews shows us what mature Christians had attained.
For it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have become partakers of the Holy Spirit,
and have tasted the goodness of the word of God and the powers of the age to come (Hebrews 6:4-5).
Christians have been enlightened with the truth, have tasted the heavenly gift, partaken of the Holy Spirit, tasted the goodness of the word of God and the powers of the age to come. Christians, do you still possess all these? Have our daily chores eroded these precious promises and gifts of God?
In real world, there are Christians who have tasted these precious gifts and yet publicly turned away. The author of Hebrews found it impossible for them to repent. For those who remain, some genuinely abide in Jesus and some simply want to take advantage of the Church. Don't lose heart. The author of Hebrews was very understanding.
For God is not so unjust as to overlook your work and the love which you showed for his sake in serving the saints, as you still do.
And we desire each one of you to show the same earnestness in realizing the full assurance of hope until the end,
so that you may not be sluggish, but imitators of those who through faith and patience inherit the promises (Hebrews 6:10-12).
The author's words are very encouraging. Persevere till the end and we will inherit the promises. Sooner or later, some will fall away.

Dear Lord, grant us the ability to discern good from evil. Strengthen us to put Your word into practice and stand firm in face of challenges. Lead us not into temptation but deliver us from evil. Amen.