What is worship? Worship in the Old Testament is laying a sacrifice upon the altar. The first time the word worship appear in the Old Testament it says, “Stay here with the donkey,” Abraham told the servants. “The boy and I will travel a little farther. We will worship there, and then we will come right back.” (Gen 22:5). Abraham was going to make a sacrifice before the Lord and he called it worship. Jesus was talking to a Samaritan woman and she asked, "tell me, why is it that you Jews insist that Jerusalem is the only place of worship, while we Samaritans claim it is here at Mount Gerizim, where our ancestors worshiped?” (John 4:20). Jesus answered and said, "the time is coming when it will no longer matter whether you worship the Father on this mountain or in Jerusalem... when true worshipers will worship the Father in spirit and in truth. The Father is looking for those who will worship him that way." (John 4:21-23)
The Old Testament people "worship only at the altar in Jerusalem" (2Kings 18:22). This was the religiously approved way to worship God. Worship was done at the altar in Jerusalem, it was done by setting up sacrifice before the Lord at the altar. But that was the old system, Jesus said we are now in a new system where worship is done by going into the spiritual reality (which is Christ) and worship God the way it is done in this reality. This brings us to the question; how is worship done in this reality? It is done by going in the spirit into the capital of the world and placing the acceptable sacrifice there. The acceptable sacrifice in this new reality is non other than Christ. The capital of world is of course the new Jerusalem where we are born and where we live.as spiritual people. So we in the spirit place ourselves sacrifice in Christ upon the altar before God - that is worship.
Let make this more practical and bring it to singing as a form of worshiping God. Worship is not just about singing neither is it about the kind of song being sang but it is utterly spiritual. Behind the singing something is happening in the spirit and that thing cannot be called worship except it involves placing the acceptable sacrifice on the altar. We worship God through prayer and singing when we reach out into the spirit with sincerity of heart and search for Christ - Christ is that which is given by God to us. So we search the spirit because the Holy Spirit is already putting in our our spirit desires, cry, desperation, hunger or revelation. For example the Holy Spirit might be putting in our heart the impression of the goodness of God or the love of God or an hunger for God or the glory and majesty of God or a revelation of our rest and sufficiency in God or etc or it could be the combination of several of these things. Whatever it is that the Holy Spirit place in our heart we take it (for it is Christ) and we sacrifice it on the altar. We sacrifice it by simply expressing it; speaking it as we pray or singing it in our songs of worship. And as we do this God accepts our sacrifice and give us more of Himself i.e the Holy Spirit would give us more of Christ. If Christ in this case is the greatness of God (if what the Holy Spirit is putting in your heart is the impression of the greatness of God) that Christ would continue to expand or magnify as long as the worship continue. That impression of God's greatness would continue to expand in your heart until it become so great that you feel like you are being crush by the impression of His greatness. This increase or expansion is embedded in the principle of tithe and giving i.e the more we give or sacrifice onto God the more God gives us back. This impression of God's greatness as given by the Spirit would magnify to be so great that you would lose sight of everything, everything would lose it significant before your eyes and all you would see is the greatness of God. Suddenly you realize that all that matters is that God is great and every other thing is useless - you are crush under the impression of His greatness. This is worship.
But this does not only apply to singing and praying as a form of worshiping God, it applies to every form of worshiping God. For example as a Christian you can feel an hunger in your heart to know God. You respond to this by placing it on the altar i.e you express this hunger by reading the Bible, listening to Christian messages, reading Christian books etc. As you offer up this sacrifice before God He accept it and reward it by giving you more hunger for the knowledge of Him. Suddenly you realize you are even more hungry to know Him, instead of holding back this hunger you offer it to God again by expressing it. The hunger increases the more, you find yourself going deep and deep in the knowledge of Him and getting more and more obsess with knowing God. Then you are possess with the hunger for the knowledge of God. Everything you do is an expressing of that hunger. This is how to live a life of worship. It is applicable not only in the hunger for the knowledge of God but also in the experience of God's love, the expression of His righteousness, the desire to lean upon Him and find sufficiency in Him, the hunger to fellowship with the brethren, the hunger to share God's word, the hunger to see lost souls saved, the hatred for carnality, the anger against sin and darkness etc. If only we learn to worship God in this way we would grow in all the fullness of God. For this is the sacrifice that God wants from us, it is denial yourself in order to express that which the Holy Spirit have put in you which is Christ the acceptable sacrifice. This is the the New Testament way of worship and it is utterly spiritual.