You worship what you do not know; we worship what we know, for salvation is from the Jews. But the hour is coming, and is now here, when the true worshipers will worship the Father in spirit and truth, for the Father is seeking such people to worship him. God is spirit, and those who worship him must worship in spirit and truth.
Being sisters, they were raised in the same Christian home and attended the same church for years. Once a week they would have Bible study with their parents, and they learned the same truths about the same God. Interestingly, they would grow to debate often about spiritual things as they became older. One would reconcile certain worldly or cultural beliefs with the scriptures while the other could not see the validity of her argument. Eventually, it became clear to the younger sister why they disagreed on so many spiritual points. The older sister, who once had known the one true God very well, was now worshiping a god of her own creation.
The words of Jesus above were true of so many religious people of his day, and they unfortunately are true today. One could argue that these words will become more and more relevant as we approach his second coming. There are those who worship the one true God, those who clearly worship a false god, and those who claim to worship the one true God but have been worshiping a god of their own making. Those of whom Jesus speaks are the ones who will worship honestly the God whom the scriptures describe. They will accept his truths instead of inventing their own truths. These worshippers not only will see clearly but also will choose the Lord no matter how difficult that choice may seem.
One great point Jesus made during his ministry was that those who honestly knew the Father would know him because He was sent by the Father. If the religious leaders of his day had known the Father, then they would have accepted the claims of Christ instead of rejecting them. To say that a Christian is worshiping in truth means that the worship is pure. That person accepts the truth of who and what God is, of what He represents, and lives according to those standards. When we decide that God is anything other than what He says He is, then our worship becomes dishonest and untruthful. Father, cause your truth to direct our acts of worship that we would come to now You exactly as You are.