“At thy right hand there are pleasures for evermore” (Ps. 16:11)
“Behold, I will make them of the synagogue of Satan, which say they are Jews, and are not, but do lie; behold, I will make them to come and worship before thy feet, and to know that I have loved thee” (Rev. 3:9).
Throughout the Old Testament a distinction is made between those Jews who knew the Lord, and those who knew the Lord in truth. This same theme is carried over into the New Testament and highlighted there, with the intent that Christians, who are members of the new Israel, would take the central lesson to heart—which is that you must be born again. Regardless of your covenant status, you must have the root of the matter within you. And the root of the matter is Christ within you, the hope of glory.
Put bluntly, if you have the covenant of God, but you do not have God Himself, then what you actually have is Satan. Nominal Christians are not partial Christians, but rather devil-worshipers. Nominal Christians are not halfway to Heaven, but rather most of the way to Hell. They are Christians in some sense, but not in any sense that is a blessing.
John here speaks fiercely of those who claimed to be Jews, but who were not. They were lying about it—whether or not they had actually descended from Abraham. They claimed they were Jewish, and they gathered in synagogues, but the whole thing was a pretense and farce.
God responds by saying that He will make them acknowledge that the Christians were the true objects of God’s electing love, which would mean that they were the heirs of all God’s promises to Israel. He would make them come and prostrate themselves before them, not in worship (as though they were divine), but rather in awe and profound respect.