Jude speaks in his epistle of three people who were religious, but not spiritual - Cain, Balaam and Korah (Jude 11). Let us consider them one by one.
Cain was not a godless man. He was a deeply religious man who believed in offering sacrifices to God (Gen. 4:3). Abel also offered sacrifices to God. But the difference between the two sacrifices and between Cain and Abel was the difference between hell and heaven, the difference between religiosity and spirituality. Cain and Abel symbolise two ways in which people have trodden - the way of religiosity and the way of spirituality. Cain is a type of those who offer external things to God - money, services, time, etc. Abel, on the other hand, symbolically laid himself on the altar when he killed the lamb and laid it on the altar.
Religious people can give gifts, pray, and do many good works - but they do not understand what it is to offer themselves. They may pay their tithes exactly, but they will not put their self to death in the moments of temptation. That is the difference between the old and the new covenants. You could enter the old covenant without dying to self. But it is impossible to enter the new covenant without dying to self. Jesus did not come to offer tithes, but to give Himself as an offering acceptable and well-pleasing to God. Cain and Abel symbolise the broad and narrow ways of approaching God - the way of religiosity and the way of true spirituality. You can be a servant without death to self. But you cannot be a son without it.
God answered Abel's sacrifice with fire from heaven. But nothing fell on Cain's offering. When a man consistently dies to self, day after day, there will be a fire from heaven on his life and on his ministry. This is the genuine baptism of the Spirit and fire that John the Baptist said Jesus would give to those whose roots He had first axed. On the other hand, a brother who merely does the right things externally may have a good life, but the fire and the anointing of heaven will be missing from his life. Satan's counterfeit 'baptism' which tickles the emotions (which is what most are enjoying today) is worthless garbage compared with the genuine baptism of the Spirit and fire that Jesus sends upon His disciples who choose the way of the cross.
Balaam was another religious man. He was a preacher who wanted to serve God, but who was also interested in making money and meeting great men in the world (Num. 22). He sought honour and financial gain for himself in the name of the Lord. There are many, many false prophets, like Balaam today. Their doctrines are all fundamentally right, according to the letter of the word. But undiscerning believers cannot recognise that they are motivated by the spirit of Balaam (loving money and honour). These are the ones about whom Paul writes in Philippians 2:21 saying that they all seek after their own interests. There were people in the church in Pergamum who lived by this doctrine of Balaam (Rev. 2:14). There is no difference between seeking for honour and seeking for money in the church. Both are but different variations of the same spirit of Balaam.
Korah was another religious man. He was from the priestly tribe of Levi (Num. 16). But he was dissatisfied with the ministry allotted to him by the Lord. He desired to be more prominent, like Moses was. This covetousness (cloaked with a religious garb) was what proved to be his destruction finally. He and his co-rebels, Dathan and Abiram, and their families, are the only ones recorded in Scripture who went alive into hell (Num. 16:32,33). So seriously did the Lord take this sin of rebellion against the authority that He Himself had appointed over His people.
Most elders, preachers and pastors today are self-appointed. To rebel against them may not be serious. It may sometimes even be necessary! But to rebel against one who has been appointed by God would bring upon one the severest judgment of God. A spiritual man would never even dream of doing such a thing. But religious people will. Such is the spiritual foolishness that accompanies religiosity.
Korah symbolises those who are in an unhealthy competition with others in the church. When you find it difficult to praise and appreciate a God-fearing brother, it is an indication that you have something of the spirit of Korah in you. When you criticise him, then you are full of the spirit of Korah. If you can listen to others criticising him, then you are like the 250 rebels who joined Korah, and who were also judged by God.
We can never become spiritual if we do not discern between religiosity and spirituality. It is the need of the hour - for it is concerning the last days that it is written that many would have the form of godliness, without the power (which is the word of the cross).